Pneumatic tire and process for production thereof

ABSTRACT

A pneumatic tire having an air permeation preventive layer comprising (A) a thin film of at least one aliphatic polyamide resin wherein at least part of the amide groups thereof are modified with alkoxyalkyl groups, (B) a thin film obtained from the curing a liquid composition containing (i) a multi component copolymer polyamide resin, (ii) a curable resin, and (iii) a curing agent for curing the curable resin, (C) a thin film obtained by coating and cross-linking a polymer composition containing (i) at least one aliphatic polyamide resin wherein at least part of the amide groups thereof are modified with alkoxyalkyl groups and/or groups having curable unsaturated bonds and (ii) at least one cross-linking agent and/or curable resin other than an acid, or (D) a thin film of a vinylidene chloride-acrylonitrile copolymer obtained by copolymerizing 5 to 50 molar % of acrylonitrile.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pneumatic tire having a layer forpreventing of air permeation which enables a reduction in the weight ofthe tire and is superior in bonding with a rubber layer, withoutdetracting from the retention of air pressure in the tire and alsorelates to a process for the production of the same.

The present invention further relates to a pneumatic tire having a layerfor preventing of air permeation which enables a reduction in the weightof the tire, is superior in bonding with the rubber layer, and, insuperior in water resistance, heat resistance, and, in some cases,durability etc., without detracting from the retention of air pressurein the tire and also relates to a process for the production of thesame.

2. Description of the Related Art

The reduction of fuel consumption is one of the major technical problemsto be solved in the automobile industry. There have been increasinglystronger demands for reduction of the weight of the pneumatic tires aspart thereof.

The inner surface of a pneumatic tire is provided with an inner linerlayer composed of a low gas-permeable rubber such as halogenated butylrubber so as to enable the tire air pressure to be kept constant. Ahalogenated butyl rubber, however, suffers from a large hysteresis loss.For this reason, when, after vulcanization of the tire, there are wavesformed in the inner surface rubber of the carcass layer and the innerliner layer in the space between the carcass cords, the inner linerrubber layer deforms along with the deformation of the carcass layer.Thus there is the problem that the rolling resistance increases.Therefore, in general, the inner liner layer (e.g., halogenated butylrubber) and inner surface rubber of the carcass layer are joined througha rubber sheet which is called a tie gum with a small hysteresis loss.Accordingly, in addition to the thickness of the inner liner layer ofthe halogenated butyl rubber, there is added the thickness of the tiegum and the layer as a whole becomes a thickness of over 1 mm (i.e.,1000 μm). As a result, this becomes one factor increasing the weight ofthe final tire product.

Various proposals have been made for using various materials, in placeof the low gas-permeable rubber such as butyl rubber, as the inner linerlayer or other air permeation preventive layer of the pneumatic tire.For example, Japanese Examined Patent Publication (Kokoku) No. 47-31761discloses the coating of the inner surface of a vulcanized tire from 0.1mm or less of a solution or dispersion of a synthetic resin such aspolyvinylidene chloride, a saturated polyester resin, or a polyamideresin having an air permeation coefficient (cm³ (standardstate)/cm·sec·mmHg)) of not more than 1.0×10⁻¹² or less at 30° C. and of5.0×10⁻¹² or less at 70° C.

The techniques disclosed in this publication provide the inner surfaceof the carcass of a vulcanized tire or the inner surface of the innerliner with a coating of a synthetic resin having a specific airpermeation coefficient and making the thickness of the synthetic resincoating 0.1 mm or less, but the pneumatic tire disclosed in thepublication had a problem in the bonding between the rubber andsynthetic resin and further had a defect that, when a polyamide resinwas used as the inner liner layer, the heat resistance and moistureresistance (or water resistance) were poor. Note that this publicationdid not disclose the use of an alkoxyalkylated polyamide, multiplecopolymer polyamide resin, alkoxyalkylated polyamide, etc.

Several proposals have been made for using a vinylidene chloride resinfor an air permeation preventive layer of a pneumatic tire. For example,Japanese Examined Patent Publication (Kokoku) No. 47-31761 proposes atube-less tire which is coated with a synthetic resin such as avinylidene chloride resin and discloses a vinylidene chloride-acrylester copolymer. Further, Japanese Unexamined Patent Publication (Kokai)No. 5-278409 proposes to construct an inner liner layer by coating athin film or solution of a vinylidene chloride-vinyl chloride copolymeron the inner surface of a tire, followed by vulcanizing. A vinylidenechloride-vinyl chloride copolymer, however, has a Tg of 40° C. or lessand is inferior in long term heat resistance, and therefore, is notsuitable for long term use at temperatures of, for example, about 80° C.A vinylidene chloride-vinyl chloride copolymer includes a large amountof chlorine, and therefore, easily degrades under heat. Further, most ofthem include up to 10% by weight of plasticizers for improving theworkability or processability, but these plasticizers shift and the filmhardens and the physical properties deteriorate. Thus there is theproblem that they are not practical.

Japanese Unexamined Patent Publication (Kokai) No. 5-330307 discloses tohalogenate the inner surface of the tire (using a conventionally knownchlorination solution, bromine solution, or iodine solution) and form ontop of that a polymer coating (thickness of 10 to 200 μm) ofmethoxymethyl nylon, a copolymer nylon, a blend of polyurethane andpolyvinylidene chloride, or a blend of polyurethane and polyvinylidenefluoride. This publication, however, discloses the use of an acidcatalyst composed of an organic acid such as citric acid or tartaricacid as a cross-linking catalyst for curing the methoxymethylated nylon,but such an acid catalyst causes the problem of an inferior flex fatiguedue to deterioration after curing and of early cracking during use andit is difficult to say that the bondability is sufficient either.Further, the art disclosed in the publication suffers from the problemof a poor moisture resistance (or water resistance) or heat resistanceof the air permeation preventive layer when an uncrosslinked or uncuredpolyamide resin is used, as the inner liner layer due to thenon-crosslinking or curing thereof.

Further, Japanese Unexamined Patent Publication (Kokai) No. 5-318618discloses a pneumatic tire having a thin film of methoxymethylated nylonas an inner liner. According to this proposal, the inner surface of agreen tire is sprayed or coated with a solution or emulsion ofmethoxymethylated nylon, then the tire is vulcanized or alternativelythe inner surface of a vulcanized tire is sprayed or coated with asolution or emulsion of methoxymethylated nylon so as to produce apneumatic tire. However, since there is no treatment for bonding betweenthe rubber of the inner surface of the tire and the methoxymethylatednylon, when the tire is used at a high load, there are still the problemthat the methoxymethylated nylon film peels off from the rubber of theinner surface of the tire and the problem that the resistance tohumidity (or water resistance) and heat resistance of the inner linerlayer are poor due to the fact the methoxymethylated nylon is notcross-linked or cured.

SUMMARY OF THE INVENTION

Accordingly the object of the present invention is to provide apneumatic tire using an air permeation preventive layer which enablesthe tire to be made lighter and which is bondable with a rubber layer,without detracting from the retention of air pressure by the tire and aprocess for production thereof.

Another object of the present invention is to provide a pneumatic tirehaving an air permeation preventive layer which enables the tire to bereduced in weight and is superior in the bonding with the rubber layerand in the water resistance and heat resistance, without detracting fromthe retention of air pressure by the tire.

In accordance with the present invention, there is provided a pneumatictire having an air permeation preventive layer comprising (A) a thinfilm of at least aliphatic polyamide resin wherein at least part of theamide groups thereof are modified with alkoxyalkyl groups, (B) a thinfilm obtained from the curing of a liquid composition comprising (i) amultiple copolymer polyamide resin, (ii) a curable resin, and (iii) acuring agent for curing the curable resin, (C) a thin film obtained fromthe coating and cross-linking of a polymer composition containing (i) atleast one type of aliphatic polyamide resin, wherein at least part ofthe amide groups thereof are modified by alkoxyalkyl groups and/orgroups having curable unsaturated bonds and (ii) at least onecross-linking agent and/or curable resin other than an acid, or (D) athin film of a vinylidene chloride-acrylonitrile copolymer obtained bycopolymerizing 5 to 50 molar % of acrylonitrile.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be better understood from the descriptionset forth with reference to FIG. 1, which is a semi-cross-sectional viewalong the meridian direction showing the structure of an inner linerportion of a pneumatic tire of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be explained in further detail.

The air permeation preventive layer of the pneumatic tire according tothe present invention may be arranged at any location inside the tire,that is, at the inside or outside of the carcass layer or at the insideor outside of the rubber layer provided adjoining the carcass layer orany other location. The point is that there is no problem if it isarranged so as to prevent the permeation and dispersion of air from theinside of the tire and enable the air pressure inside the tire to bekept for a long period of time.

FIG. 1 is a semi-cross-sectional view along the meridian directionillustrating a typical example of the arrangement of an air permeationpreventive layer of a pneumatic tire. In FIG. 1, a carcass layer 2 spansbetween the left and right bead cores 1. On the tire inner surface atthe inside of the carcass layer 2 is provided with an inner liner layer3. The inner liner layer 3 is composed from the cured or cross-linkedfirst or second composition in the present invention. In FIG. 1, 4 showsa sidewall.

According to the first aspect of the present invention, there isprovided a pneumatic tire comprising, as an air permeation preventivelayer laminated through an adhesive, a thin film of at least onealiphatic polyamide resin wherein at least part of the amide groups aremodified by alkoxyalkyl groups.

According to the first aspect of the present invention, there is furtherprovided a process for producing a pneumatic tire comprising spraying orcoating an adhesive to the surface of a carcass layer of a green tirecomposed of unvulcanized rubber or the surface of a rubber layerprovided at the surface of the carcass layer, then spraying or coatingthe adhesive surface with a liquid composition containing at least onealiphatic polyamide resin wherein at least part of the amide groups aremodified by alkoxyalkyl groups, and then vulcanizing the green tire.

According to the first aspect of the present invention, there is furtherprovided a process for producing a pneumatic tire comprising spraying orcoating an adhesive to the surface of a carcass layer of a vulcanizedtire or the surface of a rubber layer provided at the surface of thecarcass layer, then spraying or coating the adhesive surface with aliquid composition containing at least one aliphatic polyamide resinwherein at least part of the amide groups are modified by alkoxyalkylgroups.

According to the first aspect of the present invention, there is stillfurther provided, as an air permeation preventive layer laminatedthrough an adhesive, a pneumatic tire comprising a thin film of analiphatic polyamide resin obtained from the cross-linking by heattreatment in the presence of an acid catalyst at least one aliphaticpolyamide resin wherein at least part of the amide groups are modifiedwith alkoxyalkyl groups.

According to the first aspect of the present invention, there is stillfurther provided a process for producing a pneumatic tire comprising:spraying or coating an adhesive to the surface of a carcass layer of agreen tire composed of unvulcanized rubber or the surface of a rubberlayer provided at the surface of the carcass layer, then spraying orcoating the adhesive surface with a solution composed of a liquidcomposition containing at least one aliphatic polyamide resin wherein atleast part of the amide groups are modified by alkoxyalkyl groups and anacid catalyst, then vulcanizing the green tire.

According to the first aspect of the present invention, there is stillfurther provided a process for producing a pneumatic tire comprising:spraying or coating an adhesive to the surface of a carcass layer of avulcanized tire or the surface of a rubber layer provided at the surfaceof the carcass layer, then spraying or coating the adhesive surface witha solution comprising a liquid composition containing at least onealiphatic polyamide resin wherein at least part of the amide groups aremodified with alkoxyalkyl groups and an acid catalyst.

According to the first aspect of the present invention, there is stillfurther provided a pneumatic tire having an air permeation preventivelayer obtained by coating a polymer composition containing (i) at leastone aliphatic polyamide resin wherein at least part of the amide groupsare modified with alkoxyalkyl groups and/or groups having curableunsaturated bonds and (ii) at least one cross-linking agent and/orcurable resin on the surface of the carcass layer of a pneumatic tire orthe surface of a rubber layer provided on the surface of the carcasslayer, followed by cross-linking.

According to the first aspect of the present invention, there is stillfurther provided a process for producing a pneumatic tire having an airpermeation preventive layer comprising: spraying or coating an adhesiveto the surface of a carcass layer of a green tire composed ofunvulcanized rubber or the surface of a rubber layer provided at thesurface of the carcass layer, then spraying or coating the adhesivesurface with a polymer composition containing (i) at least one aliphaticpolyamide resin wherein at least part of the amide groups thereof aremodified with alkoxyalkyl groups and/or groups having curableunsaturated bonds and (ii) at least one cross-linking agent and/orcurable resin, then vulcanizing the green tire.

According to the first aspect of the present invention, as the aliphaticpolyamide resin, a modified aliphatic polyamide resin wherein at leastone amide group thereof is modified with (i) an alkoxyalkyl group and/or(ii) a group having a curable unsaturated bond is used.

The modified aliphatic polyamide resin used in the first aspect of thepresent invention, as mentioned above, is one wherein at least part ofthe amide groups thereof are modified with an alkoxyalkyl group --R¹--O--R² (wherein, R¹ is a C₁ to C₄ alkylene group, for example, amethylene, ethylene, propylene, or butylene group, R² is a C₁ to C₄alkyl group, for example, methyl, ethyl, propyl, or butyl group) and/ora group having a curable unsaturated bond as mentioned below.

Examples of the group having a curable unsaturated bond anN-methylol-acrylamide group, acryloyl group, methacrylol group, vinylgroup, allyl group, etc. these groups may be introduced by, for example,a reaction between an unsaturated acid chloride and >NH group of theamide group or a reaction with an N-methylol compound having anunsaturated bond.

The alkoxyalkyl group may be introduced by the method of reactingmethanol and para-formaldehyde with the >NH group of a polyamide in thepresence of an alkali catalyst.

Further, the alkoxyalkyl group and unsaturated bond may besimultaneously given. For example, they may be obtained by the method ofreacting an unsaturated acid chloride to the >NH group of a polyamide toform a relatively stable >N--CO-bond, then alkoxyalkylating theremaining >NH groups or the method of effecting a dehydrogenation ordealcoholization reaction, that is, a condensation reaction, betweenthe >NH group of the polyamide and an N-methylolate or N-alkoxyalkylatehaving an unsaturated bond having a good reactivity with polyamides tointroduce an unsaturated bond in the side chain of the polyamide andfurther alkoxyalkylating the remaining >NH groups.

As the polyamide, for example, linear polyamides, which are calledordinary nylons such as nylon 6, nylon 66, nylon 11, nylon 610, nylon612, nylon 10, and nylon 6/66 and polymers having --NH₂ groups in theside chains thereof are extremely useful. Examples of the unsaturatedacid chlorides are acrylic acid chloride, methacrylic acid chloride,crotonic acid chloride, and cinnamoyl chloride. Further, as theN-methylolate having the unsaturated bond are N-methylolacrylamide,N-methylolmethacryl-amide, etc. Further, examples of theN-alkoxyalkylate having an unsaturated bond areN-methoxymethylacrylamide, N-butoxymethylacrylamide, etc.

Further, when alkoxyalkylating the remaining >NH groups or --NH₂ groups,the remaining groups are made to react with aldehydes, for example,formaldehyde, acetoaldehyde, etc. and alcohols, for example, methanoland ethanol.

The cross-linkable elastic polyamide usable in the present invention andproduced by these methods is used in an amount not detracting from thepliability suitable for a cross-linked article, that is, is madepreferably 50% or less, further, more preferably 3 to 20%. Further, theflexibility given by the N-alkoxyalkylization must be stopped at theextent at which the physical properties are practical. It is preferableto use one with an N-substitution rate of 30 to 50%.

The group having the unsaturated bond, for example, as disclosed inJapanese Unexamined Patent Publication (Kokai) No. 51-24677, page 2,left bottom column to right top column, is introduced into the polyamideresin by immersing a polyamide resin such as nylon 6 into an aqueoussolution of N-methylol-acrylamide, ammonium chloride, and hydroquinone(or copper chloride), followed by drying and heat treating, washing withwater and drying, then dissolving the reaction product in formic acidcontaining phenol therein, and adding thereto a formalin solutioncontaining therein methanol, KOH, para-formaldehyde, or oxalic acid.

The modified aliphatic polyamide resin usable in the first aspect of thepresent invention is dissolved in a solvent when it is to be coated. Thesolvent is not particularly limited so long as it is a solvent whichdissolves the modified aliphatic polyamide resin. Examples of such asolvent are aliphatic alcohols such as methanol and ethanol and aromaticalcohols such as phenol and cresol etc. Further, to these alcoholsolvents, water, ethyl acetate, toluene, methyl ethyl ketone, benzene,chloroform, etc. can be added. The concentration of the total amount ofthe modified aliphatic polyamide resin and cross-linking agent, curableresin, and curing agent for the curable resin is not particularlylimited, but is preferably 5 to 30% by weight.

Examples of the acid catalyst which may be used for cross-linking themodified aliphatic polyamide resin in the first aspect of the presentinvention are one or more acids selected from the group consisting ofcitric acid, tartaric acid, glutamic acid, lactic acid, itaconic acid,azelaic acid, succinic acid, glycolic acid, crotonic acid,hypophosphorous acid, lauric acid, chloroacetic acid, boric acid, maleicacid, oxalic acid, adipic acid, and malonic acid. An aromatic sulfonicacid may also be suitably used. Examples of such an aromatic sulfonicacid are one or more acids selected from the group consisting ofp-toluenesulfonic acid, o-toluene-sulfonic acid, m-toluenesulfonic acid,benzenesulfonic acid, p-cresolsulfonic acid, o-cresolsulfonic acid,m-cresolsulfonic acid, naphthalenesulfonic acid, anddodecylbenzenesulfonic acid. The amount of the acid catalyst used may beas in the past, preferably is 3 to 5 parts by weight, based on 100 partsby weight of the modified aliphatic polyamide.

Examples of the cross-linking agents other than acid catalysts which maybe used for cross-linking the modified aliphatic polyamide resin in thefirst aspect of the present invention are sulfur alone, sulfur-releasingcompounds (e.g., tetramethylthiuram disulfide, morpholine disulfide,tetraethylthiuram disulfide, tetrabutylthiuram disulfide,dipentamethylenethiuram pentamethylene, dimethyldiphenylthiuramdisulfide), rubber vulcanization accelerators (e.g., thiazoles such as2-mercaptobenzothiazole, dibenzothiazyl-disulfide,2-mercaptobenzothiazole zinc salts, and dithio acid salts such asdichlorohexyl-benzothiazyl-sulfenamide, thiurams such astetramethylthiuram disulfide, tetramethylthiuram monosulfide,tetraethylthiuram disulfide, and dipentamethylenethiuram tetrasulfide,and zinc dimethyldithiocarbaminate, guanidines such asdiphenylguanidine, thioureas such as 1,3-diphenylthiourea), etc. Notethat the thiurams may also be used jointly as vulcanizationaccelerators. The amount of these cross-linking agents used is notparticularly limited as in the past, but preferably, depending on thetype of the cross-linking agent used, is 0.1 to 10 parts by weight, morepreferably 0.1 to 5 parts by weight, based on 100 parts by weight of thepolymer. Note that in addition to the above-mentioned crosslinkingagents, it is also possible to use peroxides such as dicumylperoxide(DCP).

For the cross-linking agent, to smooth the cross-linking reaction, it ispossible to use jointly an organic halogen donor (e.g., chlorosulfonatedpolyethylene or chloroprene) or an inorganic halogenated substance(e.g., stannous chloride, calcium chloride, iron chloride, aluminumchloride, zinc chloride, calcium fluoride, zinc bromide), etc. in anamount of 0.1 to 5 parts by weight, based on 100 parts by weight of thepolymer.

Examples of the curable resin which may be used for curing the modifiedaliphatic polyamide resin in the first aspect of the present inventionare epoxide compounds, which may be freely selected from glycidylethers, epoxyurethane resins, glycidyl ether-esters, glycidyl aminelinear aliphatic epoxy resins, aliphatic epoxy resins, etc. As thecuring agent for the curable resin, it is possible to use various typesof curing agents such as aromatic amines, acid anhydrides, polyamides,aliphatic amines, latent curing agents, etc., but generallymeta-phenylenediamine, diaminodiphenylmethane, anhydrous maleic acid,pyromellitic acid anhydrides, hexahydro anhydrous phthalic acid, andother phthalic acid anhydrides, hexamethylene diamine, etc. and alsosebacic acid dehydrazide, dicyandiamide, piperadine sebacic acid salts,etc. may be used. The curable resin, while differing depending on thecombination with the curing agent, is preferable present in an amount of60 parts by weight or less, based on 100 parts by weight of thecross-linkable elastic polyamide.

To cross-link the modified aliphatic polyamide resin in the first aspectof the present invention, it is possible to further use an alkylphenolformalin resin or alkylresorcinol formalin resin such as described, forexample, in Japanese Unexamined Patent Publication (Kokai) No. 51-18756,page 3, top left column to page 4, top right column.

The first production process of the pneumatic tire according to thefirst aspect of the present invention will be explained with referenceto the case where the inner liner layer 3 is arranged at the inside ofthe carcass layer 2, as shown in FIG. 1, the inner surface of thecarcass layer of a green tire comprising unvulcanized rubber is coatedwith an adhesive, then the top thereof is sprayed or coated with atleast one aliphatic polyamide resin wherein at least part of the amidegroups are modified with alkoxyalkyl groups, then the green tire isvulcanized by an ordinary method, whereby the desired light weightpneumatic tire is produced. Note that the same procedure may be followedwhen providing the inner liner layer at the outer circumference of thecarcass layer.

On the other hand, when the air permeation preventive layer is arrangedat the surface (that is, the inner circumference) of the carcass layerof a vulcanized tire in accordance with the present invention, thesurface of the vulcanized carcass layer which has been vulcanized by anordinary method is coated with an adhesive, then the top thereof issprayed or coated with at least one aliphatic polyamide resin wherein atleast part of the amide groups have been modified with alkoxyalkylgroups and the assembly is heated, whereby the desired light weightpneumatic tire is produced.

In the production of the pneumatic tire according to the first aspect ofthe present invention, it is possible to halogenate the surface of thecarcass layer or the rubber layer on top of the same by an ordinarymethod. This halogenation treatment may be performed, for example, usinga chlorine solution, bromine solution, iodine solution, etc. forhalogenation of general rubber. As such a solution, it is possible touse an aqueous solution including chlorine, bromine, or iodine or adilute aqueous solution of 12N hydrochloric acid. Further, it ispreferable to use a dilute solution of a compound containing--N(X)C(O)-- groups (wherein X is a halogen) in an organic solvent.Specific examples of such compounds are trichloro, dichloro, ormonochloro isocyanuric acid. Use of a solution of 2 to 20% by weight oftrichloroisocyanuric acid in an organic solvent (for example a solutionof a ketone organic solvent such as methyl ethyl ketone or a solution ofan ester organic solvent such as ethyl acetate) is most preferred.

Examples of the adhesive to be coated on the surface of the carcasslayer in the production process of a pneumatic tire according to thefirst aspect of the present invention are those which undergo a bondingreaction and self-curing reaction with the rubber of the carcass layerand the resin of the air permeation preventive layer during thevulcanization by the heat of vulcanization, such as a phenol resinadhesive, a chlorinated rubber adhesive, or an isocyanate adhesive.

Preferable examples of these adhesives are phenol resin types (e.g.,Chemlock 234B made by LORD Co.), chlorinated rubber types (e.g.,Chemlock 205 made by LORD Co.), isocyanate type (e.g., Chemlock 402 madeby LORD Co.), etc.

The material of the rubber layer for bonding with the air permeationpreventive layer according to the first aspect of the present inventionis not particularly limited. Any rubber material which has beengenerally used as a rubber material for a tire in the past may be used.Examples of such a rubber are rubber compositions composed of dienerubbers such as NR, IR, BR, and SBR, halogenated butyl rubbers,ethylene-propylene copolymer rubbers, styrene elastomers, etc. to whichhave been added blending agents such as carbon black, process oil, andvulcanization agents.

The inner liner layer according to the first aspect of the presentinvention has a melting point of 80° C. or more, preferably 100° C. ormore and an air permeation coefficient of 25×10⁻¹² cc·cm/cm² ·sec·cmHg(at 30° C.) or less, preferably 5×10⁻¹² cc·cm/cm² ·sec·cmHg (at 30° C.)or less. When the air permeation coefficient is 25×10⁻¹² cc·cm/cm²·sec·cmHg (at 30° C.) or less, the thickness of the inner liner layercan be made to 1/2 or less of the thickness of the conventional innerliner layers.

On the other hand, the Young's modulus is 1 to 500 MPa, preferably 10 to300 MPa, and the thickness is 0.01 to 1.0 mm, preferably 0.02 to 0.5 mm.When the Young's modulus is less than 1 MPa, wrinkles will form at thetime of forming the tire, whereby handling will become difficult, whilewhen more than 500 MPa, it is not possible for the film to follow thedeformation of the tire during use.

According to the second aspect of the present invention, there isprovided a pneumatic tire containing an air permeation preventive layercomprising a thin film obtained from the curing of a liquid compositioncontaining (i) a multi component copolymer polyamide resin, (ii) acurable resin, and (iii) a curing agent for curing the curable resin.

According to the second aspect of the present invention, there isfurther provided a process for producing a pneumatic tire comprising:spraying or coating the liquid composition on a surface of a carcasslayer of a green tire composed of unvulcanized rubber or the surface ofa rubber layer provided on the surface of the carcass layer which hasbeen halogenated or the surface to which an adhesive has been coated, inplace of the halogenation treatment (or in addition to the halogenationtreatment), then vulcanizing the green tire, whereby an air permeationpreventive layer is formed.

According to the second aspect of the present invention, there isfurther provided a process for producing a pneumatic tire comprising:spraying or coating the liquid composition on a surface of a carcasslayer of a vulcanized tire or the surface of a rubber layer provided onthe surface of the carcass layer, which has been halogenated or thesurface to which an adhesive has been coated, in place of thehalogenation treatment (or in addition to the halogenation treatment),then curing or cross-linking the liquid composition to form the airpermeation preventive layer.

The liquid composition comprising the air permeation preventive layer inthe second aspect of the present invention, as mentioned above, includesas essential components (i) a multiple copolymer polyamide resin, (ii) acurable resin, and (iii) a curing agent for causing the curable resin tocure. Here, the multi component copolymer polyamide resin means a threecomponent or four component or greater copolymer polyamide of a specificcopolymerization ratio such as a copolyamido nylon such as nylon 6/nylon66 (for example, a copolymerization ratio of 70/30 to 50/50) and furthernylon 6/nylon 66/nylon 610, nylon 6/nylon 66/nylon 12, nylon 6/nylon66/nylon 610/nylon 12, etc. These multi component copolymer polyamideresins may be used alone or in any combination thereof. These multicomponent copolymer polyamide resins are commercially available, forexample, as CM4000, CM4001, CM8000, etc. made by Toray. These multicomponent copolymer polyamides are soluble in solvents such as loweraliphatic alcohols such as methanol, ethanol, and propanol or mixedsolvents comprised of these alcohols plus water, trichloroethylene,chloroform, carbon tetrachloride, benzyl alcohol, phenol, formic acid,acetic acid, etc. in small amounts.

The curable resin usable in the second aspect of the present inventionmay be a resin, which is nonreactive with a multi component copolymerpolyamide resin, but itself reacts to act to fix the polyamide resin inthe cured network (generally called an IPN structure). Examples of sucha curable resin are a hard epoxy resin such as a bisphenol A type epoxyresin (ELA-128 made by Sumitomo Chemical), biphenol F type epoxy resin,phenol novolak type epoxy resin, or cresol novolak type epoxy resin, asoft epoxy resin such as a urethane modified epoxy resin and flexibleepoxy resin, etc.

These curable resins can, in the state mixed with a multi componentcopolymer polyamide, improve the water resistance and heat resistance ofthe air permeation preventive layer by causing them to cure inaccordance with ordinary methods after mixing in a later explainedcuring agent to thereby cause IPN (inter penetrating polymer network) ofthe multi component copolymer polyamide so as to affix the same.

Examples of the curing agent usable for curing the curable resin in thesecond aspect of the present invention are a polyamine, polyamide amine(Sanwa Chemical's Sunmide (preferably of an amine value of at least 150)A-100, A1001, curing at 180° C.×10 minutes), acid anhydride, thiolcompound, phenol compound (resol type), imidazole compound,dicyandiamide, acid hydrazide, Louis acid, etc. In addition, a urearesin or melamine resin may be used.

The air permeation preventive layer according to the second aspect ofthe present invention is constructed by mixing in advance the multicomponent copolymer polyamide resin and curable resin in a suitablesolvent such as a lower aliphatic alcohol such as methanol, ethanol, orpropanol or a mixed solvent composed of these and a small amount ofwater, trichloroethylene, chloroform, carbon tetrachloride, benzylalcohol, phenol, formic acid, or acetic acid, adding a curing agent tocure it, then coating this (coating what is in a particle state in thesolution, then heating so that the particles melt and form a continuouslayer) or else first mixing the multi component copolymer polyamideresin and a curable resin in a solvent, adding a curing agent thereto,then coating before the processing. Further, in the case of a so-calledlatent curing agent (not curing even when mixed in advance), it ispossible to mix all of the components at one time and effect the curingat the time of vulcanization of the tire. Even a curing agent which isinsoluble in alcohol etc. may be used in the form of a suspended statein the system. The concentration of the total of the multi componentcopolymer polyamide resin, curable resin, and curing agent for thecurable resin in the solution is not particular limited so long as itdoes not adversely affect the coating etc., but preferably is about 5 to30% by weight.

Regarding the first production process of the pneumatic tire accordingto the second aspect of the present invention, the case where the innerliner layer 3 is arranged at the inside of the carcass layer 2 isexplained as shown in FIG. 1. Thus, the inner surface of the carcasslayer of a green tire comprising unvulcanized rubber is halogenated orcoated with an adhesive, the top thereof is sprayed or coated with acomposition containing (i) the multi component copolymer polyamideresin, (ii) a curable resin compatible with the multi componentcopolymer polyamide resin, and (iii) a curing agent for curing thecurable resin, then the green tire is vulcanized by an ordinary method,whereby the desired light weight pneumatic tire is produced. Note thatthe same procedure may be followed when providing the inner liner layerat the outer circumference of the carcass layer.

On the other hand, when the air permeation preventive layer is arrangedat the surface (that is, the inner circumference) of the carcass layerof a vulcanized tire in accordance with the present invention, thesurface of the vulcanized carcass layer, which has been vulcanized by anordinary method, is halogenated or coated with an adhesive, instead ofthe halogenation treatment (or in addition to the halogenationtreatment), then the top thereof is sprayed or coated with the liquidcomposition according to the present invention and heating is applied,if necessary, to effect curing, whereby the desired light weightpneumatic tire having the air permeation preventive layer is produced.

In the production process of the pneumatic tire according to the secondaspect of the present invention, it is possible to halogenate thesurface of the carcass layer by a generally performed method. Forexample, it is possible to use a chlorine solution, bromine solution,iodine solution, etc. for halogenation of general rubber. As such asolution, it is possible to make use of an aqueous solution includingchlorine, bromine, or iodine or a dilute aqueous solution of 12Nhydrochloric acid. Further, it is preferable to use a dilute solution ofa compound containing --N(X)C(O)-- groups (wherein X is a halogen) in anorganic solvent. Examples of specific examples of such compounds aretrichloro, dichloro, or monochloro isocyanuric acid. Use of a solutionof 2 to 20% by weight of trichloroisocyanuric acid in an organic solvent(e.g., a solution of a ketone organic solvent such as methyl ethylketone or a solution of an ester organic solvent such as ethyl acetate)is most preferred.

Examples of the adhesive to be coated on the surface of the carcasslayer in the production process of a pneumatic tire according to thesecond aspect of the present invention are those which undergoes abonding reaction and self-curing reaction with the rubber of the carcasslayer and the resin of the air permeation preventive layer during thevulcanization by the heat of vulcanization such as a phenol resinadhesive, a chlorinated rubber adhesive, or an isocyanate adhesive.

The preferable examples of these adhesives are phenol resin types (e.g.,Chemlock 234B made by LORD Co.), chlorinated rubber types (e.g.,Chemlock 205 made by LORD Co.), isocyanate type (e.g., Chemlock 402 madeby LORD Co.), etc.

The material of the rubber layer for bonding with the air permeationpreventive layer according to the second aspect of the present inventionis not particularly limited. Any rubber material which has beengenerally used as a rubber material for a tire in the past may be used.Examples of such a rubber are rubber compositions comprising dienerubbers such as NR, IR, BR, and SBR, halogenated butyl rubbers,ethylene-propylene copolymer rubbers, styrene elastomers, etc. to whichhave been added blending agents such as carbon black, process oil, andvulcanization agents.

The inner liner layer according to the second aspect of the presentinvention has a melting point of 90° C. or more, preferably 100° C. ormore, and an air permeation coefficient of 25×10⁻¹² cc·cm/cm² ·sec·cmHg(at 30° C.) or less, preferably 5×10⁻¹² cc·cm/cm² ·sec·cmHg (at 30° C.)or less. When the air permeation coefficient is more than 25×10⁻¹²cc·cm/cm² ·sec·cmHg (at 30° C.) the thickness of the inner liner layercan be made the thickness of the conventional inner liner layers to 1/2or less.

On the other hand, the Young's modulus is 1 to 500 MPa, preferably 10 to300 MPa, and the thickness is 0.01 to 1.0 mm, preferably 0.02 to 0.5 mm.When the Young's modulus is less than 1 MPa, then wrinkles will form atthe time of forming the tire, whereby handling will become difficult,while when more than 500 MPa, it is not possible for the film to followthe deformation of the tire during use.

According to the third aspect of the present invention, there isprovided a pneumatic tire having an air permeation preventive layerobtained by coating a polymer composition containing (i) at least onealiphatic polyamide resin wherein at least part of the amide groupsthereof are modified by alkoxyalkyl groups and/or groups having curableunsaturated bonds and (ii) at least one cross-linking agent other thanan acid and/or curable resin on the surface of a carcass layer of apneumatic tire or the surface of a rubber layer provided on the surfaceof the carcass layer which has been halogenated, followed bycross-linking and/or curing.

The cross-linked air permeation preventive layer of the polymercomposition according to the third aspect of the present inventionpreferably has a melting point of 80° C. or more, an air permeationcoefficient of 25×10⁻¹² cc·cm/cm² ·sec·cmHg (at 30° C.) or less and aYoung's modulus of 1 to 500 MPa.

In accordance with the third aspect of the present invention, there isfurther provided a process for producing a pneumatic tire having an airpermeation preventive layer comprising a thin film obtained byhalogenating the surface of a carcass layer of a green tire comprisingunvulcanized rubber or the surface of a rubber layer provided on thesurface of the carcass layer, then spraying or coating on thehalogenated surface a polymer composition containing (i) at least onealiphatic polyamide resin wherein at least part of the amide groupsthereof are modified with alkoxyalkyl groups and/or groups havingcurable unsaturated bonds and (ii) at least one cross-linking agentother than an acid and/or curable resin, and then vulcanizing the greentire.

In accordance with the third aspect of the present invention, there isfurther provided a process for producing a pneumatic tire having an airpermeation preventive layer comprising a thin film obtained byhalogenating the surface of a carcass layer of a vulcanized tire or thesurface of a rubber layer provided on the surface of the carcass layer,then spraying or coating on the halogenated surface a polymercomposition containing (i) at least one aliphatic polyamide resinwherein at least part of the amide groups thereof are modified byalkoxyalkyl groups and/or groups having curable unsaturated bonds and(ii) at least one cross-linking agent other than an acid and/or curableresin, followed by cross-linking and/or curing.

The polymer composition comprising the air permeation preventive layerin the third aspect of the preset invention, as mentioned above,includes as essential components (i) at least one aliphatic polyamideresin wherein at least part of the amide groups thereof are modified byalkoxyalkyl groups and/or groups having curable unsaturated bonds and(ii) at least one cross-linking agent other than an acid and/or curableresin. Here, examples of the aliphatic polyamide resin are nylon 6,nylon 66, nylon 610, nylon 6/nylon 66, nylon 612, nylon 8, nylon 10,nylon 11, nylon 12, etc. as well as any mixtures thereof and copolymersof two or more of these components.

According to the third aspect of the present invention, as the aliphaticpolyamide resin, as mentioned above, a modified aliphatic polyamideresin wherein at least part of the amide groups thereof are modified byalkoxyalkyl groups and/or groups having curable unsaturated bonds or amixture of at least one aliphatic polyamide resin wherein at least partof the amide groups thereof are modified with alkoxyalkyl groups and atleast one aliphatic polyamide resin wherein at least part of the amidegroups thereof are modified with groups having curable unsaturated bondsis used.

The modified aliphatic polyamide resin usable in the third aspect of thepresent invention, as mentioned above, is those wherein at least part ofthe amide groups thereof are modified with an alkoxyalkyl group --R¹--O--R² (wherein, R¹ is a C₁ to C₄ alkylene group, for example, amethylene, ethylene, propylene, or butylene group, R² is a C₁ to C₄alkyl group, for example, methyl, ethyl, propyl, or butyl group) and/ora group having a curable unsaturated bond as mentioned below.

Examples of the group having a curable unsaturated bond are anN-methylol-acrylamide group, acryloyl group, methacrylol group, vinylgroup, allyl group, etc. For example, it may be introduced by a reactionbetween an unsaturated acid chloride and >NH group of the amide group ora reaction with an N-methylol compound having an unsaturated bond.

The alkoxyalkyl group may be introduced by the method of reactingmethanol and paraformaldehyde with the >NH group of a polyamide in thepresence of an alkali catalyst.

Further, the alkoxyalkyl group and unsaturated bond may besimultaneously given. For example, they may be obtained by the method ofreacting the >NH group of a polyamide and an unsaturated acid chlorideto form a relatively stable >N--CO-bond, then alkoxyalkylating theremaining >NH group or the method of effecting a dehydrogenation ordealcoholization reaction, that is, a condensation reaction, betweenthe >NH group of the polyamide and an N-methylolate or N-alkoxyalkylatehaving an unsaturated bond having a good reactivity with polyamides tointroduce an unsaturated bond in the side chain of the polyamide andfurther alkoxyalkylating the remaining >NH groups.

As the polyamide, for example, linear polyamides, which are calledordinary nylons such as nylon 6, nylon 66, nylon 11, nylon 610, nylon612, nylon 10, nylon 12, and nylon 6/66 and polymers having --NH₂ groupsin their side chains are extremely useful. Examples of the unsaturatedacid chlorides are acrylic acid chloride, methacrylic acid chloride,crotonic acid chloride, and cinnamoyl chloride. Further, as theN-methylolate having the unsaturated bond, there are for exampleN-methylolacrylamide, N-methylolmethacrylamide, etc. Further, as theN-alkoxyalkylate having an unsaturated bond, there are for exampleN-methoxymethylacrylamide, N-butoxymethylacrylamide, etc.

Further, when alkoxyalkylating the remaining >NH groups or --NH₂ groups,the remaining groups are reacted with aldehydes, for example,formaldehyde, acetoaldehyde, etc. and alcohols, for example, methanoland ethanol.

The cross-linkable elastic polyamide usable in the present invention andproduced by these methods is preferably used in an amount not detractingfrom the pliability suitable for a cross-linked article, that is, ismade 50% or less, further, 3 to 20%. Further, the flexibility given bythe N-alkoxyalkylization must be stopped at the extent at which thephysical properties are practical. It is preferable to use one with anN-substitution rate of 30 to 50%.

The group having the unsaturated bond, for example, as disclosed inJapanese Unexamined Patent Publication (Kokai) No. 51-24677, page 2,left bottom column to right top column, is introduced into the polyamideresin by immersing a polyamide resin such as nylon 6 into an aqueoussolution of N-methylol-acrylamide, ammonium chloride, and hydroquinone(or copper chloride), followed by drying and heat treating, and furtherby washing with water and drying. Thereafter the reaction product isdissolved in formic acid containing phenol, followed by adding to aformalin solution containing methanol, KOH, para-formaldehyde, andoxalic acid.

The modified aliphatic polyamide resin usable in the third aspect of thepresent invention is dissolved in a solvent when to be coated. Thesolvent is not particularly limited so long as it is a solvent whichdissolves the modified aliphatic polyamide resin. Examples are aliphaticalcohols such as methanol and ethanol and aromatic alcohols such asphenol and cresol etc. Further, it is also possible to add to thesealcohol solvents water, ethyl acetate, toluene, methyl ethyl ketone,benzene, chloroform, etc. The concentration of the total amount of themodified aliphatic polyamide resin and cross-linking agent, curableresin, and curing agent for the curable resin is not particularlylimited, but is preferably 5 to 30% by weight.

Examples of cross-linking agents other than acid catalysts which may beused for cross-linking the modified aliphatic polyamide resin in thethird aspect of the present invention are sulfur alone, sulfur-releasingcompounds (for example, tetramethylthiuram disulfide, monopholindisulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide,dipentamethylenethiuram pentamethylene, dimethyldiphenylthiuramdisulfide), rubber vulcanization accelerators (e.g., thiazoles such as2-mercaptobenzothiazole, dibenzothiazyl-disulfide,2-mercaptobenzothiazole zinc salts, and dithio acid salts such asdichlorohexyl-benzothiazyl-sulfenamide, thiurams such astetramethylthiuram-disulfide, tetramethylthiuram monosulfide,tetraethylthiuram disulfide, and dipentamethylenethiuram tetrasulfide,and zinc dimethyldithiocarbaminate, guanidines such asdiphenylguanidine, thioureas such as 1,3-diphenylthiourea), etc. Notethat the thiurams may also be used together as vulcanizationaccelerators. The amount of these cross-linking agents used is notparticularly limited as in the past, but preferably, depending on thetype of the cross-linking agent used, is 0.1 to 10 parts by weight,based on 100 parts by weight of the polymer, more preferably 0.1 to 5parts by weight. Note that, in addition thereto, it is also possible touse peroxides such as dicumylperoxide (DCP).

For the cross-linking agent, to smooth the cross-linking reaction, it ispossible to use together an organic halogen donor (e.g.,chlorosulfonated polyethylene or chloroprene) or an inorganichalogenated substance (e.g., stannous chloride, calcium chloride, ironchloride, aluminum chloride, zinc chloride, calcium fluoride, zincbromide), etc. in an amount of 0.1 to 5 parts by weight, based on 100parts by weight of the polymer.

Examples of the curable resin which may be used for curing the modifiedaliphatic polyamide resin in the third aspect of the present inventionare a compound having an epoxy group. This may be selected from glycidylethers, epoxyurethane resins, glycidyl ether-esters, glycidylaminelinear aliphatic epoxy resins, aliphatic epoxy resins, etc. As thecuring agent for the curable resin, it is possible to use various typesof curing agents such as aromatic amines, acid anhydrides, polyamides,aliphatic amines, latent curing agents, etc., but general curing agentsare metaphenylenediamine, diaminodiphenylmethane, anhydrous maleic acid,pyromellitic acid anhydrides, hexahydro anhydrous phthalic acid, andother phthalic acid anhydrides, hexamethylene diamine, sebacic aciddehydrazide, dicyanediamide, piperadine sebacic acid salts, etc. Theamount of the curable resin used is not particularly limited, butgenerally is preferable present in an amount of 60 parts by weight orless, based on 100 parts by weight of the polyamide resin.

To cross-link the modified aliphatic polyamide resin in the third aspectof the present invention, it is possible to further use an alkylphenolformalin resin or alkylresorcinol formalin resin such as disclosed in,for example, Japanese Unexamined Patent Publication (Kokai) No.51-18756, page 3, top left column to page 4, top right column.

The first production process of the pneumatic tire according to thethird aspect of the present invention will be, explained with referenceto the case where the air permeation preventive layer (inner linerlayer) 3 is arranged at the inside of the carcass layer 2 as shown inFIG. 1. The inner surface of the carcass layer of a green tirecomprising unvulcanized rubber is halogenated in accordance with anordinary method, then the top thereof is sprayed or coated with themodified polyamide resin composition, then the green tire is vulcanizedby an ordinary method, whereby the desired light weight pneumatic tireis produced. Note that the same procedure may be followed when providingthe air permeation preventive layer at the outer circumference of thecarcass layer.

On the other hand, when the air permeation preventive layer is arrangedat the surface (that is, the inner circumference) of the carcass layerof a vulcanized tire in accordance with the present invention, thesurface of the vulcanized carcass layer which has been vulcanized by anordinary method is halogenated by a conventional method, then the topthereof is sprayed or coated with at least one modified polyamide resinaccording to the present invention and the assembly is heated andcross-link or cure, whereby the desired light weight pneumatic tire isproduced.

In the process of production of the pneumatic tire according to thethird aspect of the present invention, it is possible to halogenate thesurface of the carcass layer or the rubber layer on the top thereof byan ordinary method. This halogenation treatment may be performed, forexample, using a chlorine solution, bromine solution, iodine solution,etc. for halogenation of general rubber. Examples such a solution are anaqueous solution containing chlorine, bromine, or iodine or a diluteaqueous solution of 12N hydrochloric acid. Further, it is preferable touse a dilute solution of a compound containing --N(X)C(O)-- groups(wherein X is a halogen) in an organic solvent. Specific examples ofsuch compounds are trichloro, dichloro, or monochloro isocyanuric acid.Use of a solution of 2 to 20% by weight of trichloroisocyanuric acid inan organic solvent (e.g., a solution of a ketone organic solvent such asmethyl ethyl ketone or a solution of an ester organic solvent such asethyl acetate) is most preferred.

The material of the rubber layer for bonding with the air permeationpreventive layer according to the third aspect of the present inventionis not particularly limited. Any rubber material which has beengenerally used as a rubber material for a tire in the past may be used.Examples of such a rubber are rubber compositions composed of dienerubbers such as NR, IR, BR, and SBR, halogenated butyl rubbers,ethylene-propylene copolymer rubbers, styrene elastomers, etc. to whichhave been added blending agents such as carbon black, process oil, andvulcanization agents.

The cured or cross-linked air permeation preventive layer according tothe third aspect of the present invention has a melting point of 80° C.or more, preferably 100° C. or more, and an air permeation coefficientof 25×10⁻¹² cc·cm/cm² ·sec·cmHg (at 30° C.) or less, preferably 5×10⁻¹²cc·cm/cm² ·sec·cmHg (at 30° C.) or less. When the air permeationcoefficient is 25×10⁻¹² cc·cm/cm² ·sec·cmHg (at 30° C.) or less, thethickness of the inner liner layer can be 1/2 or less of the thicknessof the conventional inner liner layers.

On the other hand, the Young's modulus is 1 to 500 MPa, preferably 10 to300 MPa, and the thickness is 0.01 to 1.0 mm, preferably 0.02 to 0.5 mm.When the Young's modulus is less than 1 MPa, wrinkles will form at thetime of forming the tire, whereby handling will become difficult, whilewhen more than 500 MPa, it is not possible for the film to follow thedeformation of the tire during use.

According to the fourth aspect of the present invention, there isprovided a pneumatic tire having an air permeation preventive layercomprising a thin film of a vinylidene chloride-acrylonitrile copolymerformed by copolymerizing 5 to 50 molar % of acrylonitrile.

According to the fourth aspect of the present invention, there isfurther provided a process for producing a pneumatic tire comprising:spraying or coating a solution of the vinylidene chloride copolymer on asurface of a carcass layer of a green tire comprising unvulcanizedrubber or the surface of a rubber layer such as an air permeationpreventive layer composed of a low gas permeable rubber provided on thesurface of the carcass layer which has been halogenated or the surfaceto which an adhesive has been coated, in place of the halogenationtreatment (or in addition to the halogenation treatment), thenvulcanizing the green tire, whereby an air permeation preventive layeris formed.

According to the fourth aspect of the present invention, there isfurther provided a process for producing a pneumatic tire comprising:spraying or coating the solution of the vinylidene chloride copolymer ona surface of a carcass layer of a vulcanized tire or the surface of arubber layer such as an air permeation preventive layer composed of alow gas-permeable rubber provided on the surface of the carcass layerwhich has been halogenated or the surface to which an adhesive has beencoated, in place of the halogenation treatment (or in addition to thehalogenation treatment) to form an air permeation preventive layer bythe vinylidene chloride copolymer.

The vinylidene chloride copolymer comprising the air permeationpreventive layer in the fourth aspect of the present invention, asmentioned above, includes as essential components, a copolymer ofvinylidene chloride and acrylonitrile wherein the content of theacrylonitrile is 5 to 50 molar %, based on the total copolymer,preferably 10 to 35 molar %. When the content of the acrylonitrile istoo small, the result is poor in solubility in general solvents, whilewhen too large, the Young's modulus becomes higher and not only is theresult not practical, but it becomes hard to include a large amount ofacrylonitrile in the synthesis of an actual copolymer. The vinylidenechloride-acrylonitrile copolymer further may be a three-way copolymer ofvinylidene chloride, acrylonitrile, and vinyl chloride containing 5 to15 molar % of vinyl chloride.

These vinylidene chloride copolymers are, for example, soluble insolvents such as xylene, toluene, methyl ethyl ketone, andtetrahydrofuran, ester solvents such as ethyl acetate and butyl acetate,and mixed solvents of the same.

When the air permeation preventive layer is constructed in accordancewith the fourth aspect of the present invention, it is sufficient to mixthe vinylidene chloride-acrylonitrile copolymer resin in a suitablesolvent such as mentioned above and then to coat it. The concentrationof the vinylidene chloride copolymer in the solution is not particularlylimited so long as it does not hinder the coating, but preferably it is3 to 50% by weight, more preferably 5 to 30% by weight. When theconcentration is too low, the amount of the adhering resin is small andthe result is not practical, while conversely when too large, thesolution viscosity becomes high and the working or processing becomesdifficult. The vinylidene chloride-acrylonitrile copolymer in accordancewith the present invention has, with a thickness after curing of 10 to50 μm, an air permeation coefficient of 25×10⁻¹² cc·cm/cm² ·sec·cmHg (at30° C.) or less, an elongation after vulcanization of 10% or more andbefore vulcanization of 110% or more, and an elasticity of 1 to 500 MPa.As the vinylidene chloride copolymer, for 5 example, Dow Chemical'sSaran F-310 (acrylonitrile content: 30 mol %) may be used. In this case,the values are 550% and 2 MPa, respectively.

Regarding the first production process of the pneumatic tire accordingto the fourth aspect of the present invention, the case where the innerliner layer 3 is arranged at the inside of the carcass layer 2 as shownin FIG. 1, the inner surface of the carcass layer of a green tirecomprising unvulcanized rubber is halogenated or coated with anadhesive, the top thereof is sprayed or coated with the vinylidenechloride-acrylonitrile copolymer in a solution state or dispersionstates, then the green tire is vulcanized by an ordinary method, wherebythe desired light weight pneumatic tire is produced. Note that the sameprocedure may be followed when the inner liner layer is provided at theouter circumference of the carcass layer.

On the other hand, when the air permeation preventive layer is arrangedat the surface (that is, the inner circumference) of the carcass layerof a vulcanized tire in accordance with the present invention, thesurface of the vulcanized carcass layer which has been vulcanized by anordinary method is halogenated or coated with an adhesive, instead ofthe halogenation treatment (or in addition to the halogenationtreatment), then the top is sprayed or coated with the liquidcomposition according to the present invention and heating is applied,if necessary, to quickly form the thin film, whereby the desired lightweight pneumatic tire having the air permeation preventive layer isproduced.

In the production process of the pneumatic tire according to the fourthaspect of the present invention, it is possible to halogenate thesurface of the carcass layer by a generally performed method. Forexample, it is possible to use a chlorine solution, bromine solution,iodine solution, etc. for halogenation of general rubber. Examples of asolution for chlorination, are a solution of trichloroisocyanuricacid/MEK (methyl ethyl ketone) in a weight ratio of 95/5. Here, theratio of mixture of the trichloroisocyanuric acid and MEK may of coursebe changed in accordance with the application. Further, ethyl acetatemay be used, instead of MEK.

Examples of the adhesive to be coated on the surface of the carcasslayer in the production process of a pneumatic tire according to thefourth aspect of the present invention are a reactive adhesive such asthose which undergones a bonding reaction with the rubber of the carcasslayer and the resin of the air permeation preventive layer during thevulcanization by the heat of vulcanization such as a phenol resinadhesive, a chlorinated rubber adhesive, or an isocyanate adhesive.

Examples of preferable examples of these adhesives are phenol resintypes (e.g., Chemlock 234B made by LORD Co.), chlorinated rubber types(e.g., Chemlock 205 made by LORD Co.), isocyanate type (e.g., Chemlock402 made by LORD Co.), etc. The amount of the adhesive used is as in thepast and is not particularly limited.

The material of the rubber layer for bonding with the air permeationpreventive layer according to the fourth aspect of the present inventionis not particularly limited. Any rubber material which has beengenerally used as a rubber material for a tire in the past may be used.Examples of such a rubber are rubber compositions composed of dienerubbers such as NR, IR, BR, and SBR, halogenated butyl rubbers,ethylenepropylene copolymer rubbers, styrene elastomers, etc. to whichhave been added blending agents such as carbon black, process oil, andvulcanization agents.

The air permeation preventive layer according to the fourth aspect ofthe present invention has a softening point of 80° C. or more,preferably 100° C. or more, an air permeation coefficient of 25×10⁻¹²cc·cm/cm² ·sec·cmHg (at 30° C.) or less, preferably 0.05×10⁻¹² to10×10⁻¹² cc·cm/cm² ·sec·cmHg (at 30° C.) or less. When the airpermeation coefficient is 25×10⁻¹² cc·cm/cm² ·sec·cmHg (at 30° C.) orless, the thickness of the air permeation preventive layer can be made1/2 or less of the thickness of the conventional air permeationpreventive layers.

On the other hand, the Young's modulus is 1 to 500 MPa, preferably 10 to300 MPa. When the Young's modulus is less than 1 MPa, then wrinkles willform at the time of forming the tire, whereby handling will becomedifficult, while when more than, 500 MPa, it is not possible for thefilm to follow the deformation of the tire during use.

EXAMPLES

The present invention will now be further illustrated by, but is by nomeans limited to, the following Examples.

Examples I-1 to I-24 and Comparative Examples I-1 to I-3

Examples I-1 to I-11 are Examples of coating an alkoxyalkylatedaliphatic polyamide resin before vulcanization of the tire. The innersurface of a green tire molded by an ordinary method and composed ofunvulcanized rubber is spray-coated by an adhesive, dried at roomtemperature for 30 minutes, then spray-coated with a solution composedof a mixed solvent of 70% by weight of methanol and 30% by weight ofmethyl ethyl ketone in which has been dissolved an alkoxyalkylatedaliphatic polyamide resin in a proportion of 20% by weight. This isblown on by hot air of 80° C. for 2 minutes, then vulcanized by a tirevulcanizer at 185° C. for 15 minutes at a pressure of 2.3 MPa.

Examples I-12 to I-24 and Comparative Example I-3 are examples ofcoating an adhesive in the same way on the inner surface of a tirevulcanized by an ordinary method under the same type of vulcanizationconditions as above, followed by spray-coating with a solution preparedin the same way as mentioned above and cross-linking or curing inaccordance with the cross-linking and curing conditions shown in TableII.

Comparative Examples I-1 to I-2 are examples of not coating an adhesive,but halogenating the inner surface of an unvulcanized green tire orvulcanized tire (brush-coating a 3.3% solution of trichloroisocyanuricacid in ethyl acetate and drying for 2 hours). The vulcanizationconditions were similar to those mentioned above.

Further, the standard Example of a tire used a butyl rubber compositionof the following formulation as an inner liner layer:

    ______________________________________                                        Formulation of Butyl Rubber Compound                                          (Unit: Parts by Weight)                                                       ______________________________________                                        Br-IIR                100                                                     Carbon black (GPF)    60                                                      Stearic acid          1                                                       Petroleum based hydrocarbon resin*.sup.1                                                            10                                                      Paraffinic process oil                                                                              10                                                      Zinc oxide            3                                                       DM                    1                                                       Sulfur                0.6                                                     ______________________________________                                         *.sup.1 : Escorez 1102 made by Esso Chemical.                            

The methods of evaluation used in the following Examples were asfollows:

Method of Preparation of Alkoxyalkylated Aliphatic Polyamide ResinSolution Used in Tire

The polymers, cross-linking agents, and other additives shown in thefollowing formulations 1 to 8 were dissolved in a mixed solvent of 30%by weight of methyl ethyl ketone and 70% by weight of methanol to givepolymer concentrations of 30% by weight.

The formulations used were as shown in the following formulations 1 to 3and formulation 8:

    ______________________________________                                                   Formul-                                                                             Formul-   Formul- Formul-                                               ation 1                                                                             ation 2   ation 3 ation 8                                    ______________________________________                                        Polymer A.sup.*1                                                                           100     100       100   --                                       Polymer B.sup.*2                                                                           --      --        --    100                                      Sulfur       1.5     --        --    1.5                                      Peroxide (di-                                                                              --      1.0       --    --                                       cumylperoxide)                                                                Sulfur-releasing-                                                                          --      --        1.5   --                                       agent (tetra-                                                                 methylthiuram                                                                 disulfide)                                                                    DM           3.0     --        --    3.0                                      M            2.0     --        --    2.0                                      MZ           2.0     --        --    2.0                                      SnCl.sub.2   1.0     --        --    1.0                                      ______________________________________                                         .sup.*1 Polymer A: Polymer A was formulated as follows in accordance with     the method described in Japanese Unexamined Patent Publication (Kokai) No     5124657, page 3, bottom right column, Production Example (2) (parts are       parts by weight).                                                        

A 500 parts amount of nylon 6 and 2000 parts of formic acid were placedin a reactor provided with a reflux cover and were fully stirred to makea homogeneous solution. 3 parts of phenol and 10 parts ofN-methylolacrylamide were added and the stirring continued for 30minutes while holding the temperature at 70° C. During this process, theN-methylolacrylamide and >NH groups included in the nylon 6 moleculeengaged in a dehydrogenation condensation reaction.

Separately, 10 parts of KOH were added to 3000 parts of methanol held at60° C. and a homogeneous solution made, then 2500 parts ofpara-formaldehyde were added to cause complete dissolution. TheN-methoxymethylation reaction was completed, while gradually adding thisto the above nylon 6 formic acid solution.

At this time, the temperature of the reaction system became 60 to 64° C.Further, the time until the end of the addition of themethanol-para-formaldehyde solution was made 10 to 15 minutes and thereaction was made to complete in 60 minutes from the start of theaddition.

The resultant reaction solution was poured into water and the targetsubstance was removed. This was fully washed with water, then dried. Theresult was a flexible substance having a good elasticity.

A 500 parts amount of nylon 66 and 2000 parts of formic acid were placedin a reactor provided with a reflux cover and were fully stirred to makea homogeneous solution. A 3 parts amount of phenol and 10 parts ofN-methylolacrylamide were added and the stirring continued for 30minutes, while holding the temperature at 70° C. During this process,the N-methylolacrylamide and >NH groups contained in the nylon 66molecule caused a dehydrogenation condensation reaction.

    ______________________________________                                                         Formul-                                                                             Formul-                                                                 ation 4                                                                             ation 5                                                ______________________________________                                        Luckamide 5003.sup.*1                                                                            100     100                                                Epicoat #828.sup.*2                                                                              15      30                                                 (epoxide group)                                                               Sebacic acid dihydrazide                                                                           3.5     7.5                                              (curing agent)                                                                ______________________________________                                         .sup.*1 Luckamide 5003: Dainippon Ink nylon 8/nylon 6 based                   methoxymethylated aliphatic polyamide resin (amide conversion rate of at      least 28%)                                                                    .sup.*2 Epicoat #828: Bisphenol A diglycidyl ether (Shell Chemical)      

    ______________________________________                                                         Formul-                                                                             Formul-                                                                 ation 6                                                                             ation 7                                                ______________________________________                                        Luckamide 5003     100     100                                                Hitanol 1502.sup.*1                                                                              12      --                                                 Takkirol 250-1.sup.*2                                                                            --      20                                                 Zinc oxide          3       3                                                 Boric acid          1      --                                                 ______________________________________                                         .sup.*1 Hitanol 1502: Resol type phenolic resin of molecular weight of        about 800 (made by Hitachi Kasei Co.)                                         .sup.*2 Takkirol 2501: Brominated alkylphenolformaldehyde resin (made by      Taoka Kagaku Kogyo)                                                      

Preparation of Film Sample

Solutions of alkoxyalkylated aliphatic polyamide resin of theformulations of Examples and Comparative Examples dissolved in aproportion of 20% by weight in a mixed solvent of 70% by weight ofmethanol and 30% by weight of methyl ethyl ketone were formed into filmsby the film casting method (uniformly casting a polymer solution on anendless belt, continuously drying it by blowing hot air of 60 to 90° C.,then peeling to form a film). After drying, these were allowed to standin a 130° C. heater for 15 minutes for a cross-linking or curingreaction. (Film: thickness of approximately 100 μm)

Method for Measurement of Melting Point

A differential scan calorimeter (DSC) was used, the temperature raisedat 10° C./min, and the endothermic peak temperature caused by themelting point was read or, when the peak was unclear, a thermalmechanical analysis (TMA) apparatus was used, a compression test wasperformed at a load of 5 g, and the melting point was read from thetemperature of the point of inflexion.

Measurement of Air Permeation Coefficient of Air Permeation PreventiveLayer

According to JIS K7126 "Test Method of Gas Permeability of Plastic Filmsand Sheets (Method A)".

Test piece: Samples of films prepared in the examples used.

Test gas: Air (N₂ :O₂ =8:2)

Test temperature: 30° C.

Method for Measurement of Young's Modulus of Film

According to JIS K6251 "Tensile Test Method of Vulcanized Rubber".

Test piece: The film samples prepared above were punched into JIS No. 3dumbbell shapes in parallel to the direction of flow of the solution(direction of flow of endless belt). A tangent was drawn to the curve ofthe initial strain area of the resultant stress-strain curve and theYoung's modulus was found from the inclination of the tangent.

Method for Measurement of Peeling Strength of Air Permeation PreventiveLayer/Carcass Layer

According to JIS K6258 "Test Method of Bonding of Vulcanized Rubber".

Test piece: A finished tire was disassembled and short strips of a widthof 25 mm were punched out in the direction of arrangement of the carcasscord.

Test temperature: 20° C.

Test: The inner liner layer and carcass layer of a sample were partiallypeeled apart in advance. The layers of the sample were gripped in thechucks of a tensile tester and were peeled apart at the followingtensile rate: 50.0±5.0 mm/min

Method for Testing Long Term Durability

A 165SR13 steel radial tire (rim 13×41/2-J) was used, was mounted on a1500 cc class passenger car at an air pressure of 200 kPa, was subjectedto a load corresponding to four passengers (65 kg/person), and was runon actual roads for 20,000 km.

After use, the tire was removed from the rim and the liner layer at theinside surface of the tire was visually examined. Liner layers withcracks, visible wrinkles, or peeled or blistered liner layers werejudged as failing and those without them as passing.

The test was designed to evaluate as a whole the deterioration ofstrength, deterioration of bonding, etc. of the liner layer by actualcars.

Method for Testing Long Term Water Resistance and Resistance to MoistureAbsorption

A 165SR13 steel radial tire (rim 13×41/2-J) was used and run on a φ1707mm drum at a speed of 80 km/h at an air pressure of 200 kPa, a load of5.5 kN, and a room temperature of 38° C. After 10,000 km, the insidesurface of the tire was visually examined. Liner layers with cracks,visible wrinkles, or peeled or blistered liner layers were judged asfailing and those without them as passing.

Note that just before the test run, the tire was allowed to stand for 10days at a relative humidity of 98% and a room temperature of 70° C.

Method for Testing Tire Air Leakage Performance

A 165SR13 steel radial tire (rim 13×41/2-J) was used, allowed to standat an initial pressure of 200 kPa under no-load conditions at roomtemperature 21° C. for 3 months, and measured as to pressure every fourday interval.

When the measured pressure is Pt, the initial pressure is Po, and thenumber of days elapsed is t, the value α is found by recurrence of thefunction:

    Pt/Po=exp(-αt)

The α obtained is used and t=30 substituted in the following formula toobtain β:

    β=[1-exp(-αt)]×100

This value β is considered the rate of reduction of pressure per month(%/month).

    ______________________________________                                        Formulation of Rubber for Tire Carcass                                                           Parts by                                                   Ingredient           weight                                                   ______________________________________                                        Natural rubber       80.0                                                     SBR 1502             20.0                                                     FEF carbon black     50.0                                                     Stearic acid         2.0                                                      Zinc oxide           3.0                                                      Sulfur               3.0                                                      Vulcanization accelerator (NS)                                                                     1.0                                                      Aromatic oil         2.0                                                      ______________________________________                                    

The results for the evaluation are shown in Table I-1 and Table I-2.

                                      TABLE I-1                                   __________________________________________________________________________                        Stan-                                                                             Comp. Ex.                                                                 dard ex.                                                                          I-1   Ex. I-1                                                                             Ex. I-2                                                                             Ex. I-3                                                                             Ex. I-4                                                                            Ex.                                                                                Ex.                 __________________________________________________________________________                                                              I-6                 Material of air permeation preventive layer                                                       Butyl                                                                             Alkoxyalkylated aliphatic polyamide resin                                 rubber                                                    Step of coating air permeation preventive layer                                                   --  Before tire vulcanization                             Type of polyamide/Amount of polyamide                                                             --  Luckamide                                                                           Luckamide                                                                           Luckamide                                                                           Luckamide                                                                           Polymer                                                                            Polymer                                                                            Polymer B           (parts)                 100   100   100   100   100  100  100                 Method of bonding rubber and polyamide                                        Halogenation        --  Yes   --    --    --    --   --   --                  Use of adhesive     --  --    Yes   Yes   Yes   Yes  Yes  Yes                 Type of adhesive used         Chemlock                                                                            Chemlock                                                                            Chemlock                                                                            Chemlock                                                                           Chemlock                                                                           Chemlock                                          234B  205   205   402  402  234B                Cross-linking/curing of polyamide                                                                 --  Yes   No    Yes   Yes   Yes  Yes  Yes                 Cross-linking agent                                                           Acid catalyst/Amount of catalyst (parts)                                                          --  Tartaric                                                                            --    Tartaric                                                                            Citric acid 5                                                                       --   --   --                                          acid 5      acid 5                                    Other than acid     --  --    --    --    --    Form. 1                                                                            Form.                                                                              Form. 8             Air permeation coefficient of air permeation                                                      55  3.0   4.7   3.0   3.2   4.5  4.2  5.2                 preventive layer ×10.sup.-12 (cc · cm/cm.sup.2 ·      sec · cmHg) (30° C.)                                          Young's modulus of air permeation                                                                 15  252   245   252   240   275  290  380                 preventive layer (MPa) (23° C.)                                        Peeling strength of air permeation                                                                40  20    38    42    43    45   42   45                  preventive layer/carcass                                                      layer (N/cm) (23° C.)                                                  Long term durability test                                                                         Passed                                                                            Failed                                                                              Passed                                                                              Passed                                                                              Passed                                                                              Passed                                                                             Passed                                                                             Passed                                      Liner                                                                         peeling                                               Tire air leakage performance (%/month)                                                            3.0 1.9   2.7   1.9   2.0   2.6  2.5  2.9                 Thickness of air permeation preventive                                                            0.50                                                                              0.05  0.05  0.05  0.05  0.05 0.05 0.05                layer (mm)                                                                    Mass of air permeation preventive layer (g)                                                       480 48    47    48    48    48   47   48                  Melting point of air permeation preventive                                                        --  160   152   160   160   155  157  160                 layer (° C.)                                                           __________________________________________________________________________                              Standard                                                                      ex.   Ex. I-7                                                                             Ex. I-8                                                                             Ex. I-9                                                                              Ex. I-10                                                                            Ex.                  __________________________________________________________________________                                                             I-11                 Material of air permeation preventive layer                                                             Butyl Alkoxyalkylated aliphatic polyamide                                           resin                                                                   rubber                                              Step of coating air permeation preventive layer                                                               Before tire vulcanization                     Type of polyamide/Amount of polyamide (parts)                                                           --    Polymer A                                                                           Luckamide                                                                           Luckamide                                                                            Luckamide                                                                           Luckamide                                      --    100   100   100    100   100                  Method of bonding rubber and polyamide                                        Halogenation              --    --    --    --     --    --                   Use of adhesive           --    Yes   Yes   Yes    Yes   Yes                  Type of adhesive used           Chemlock                                                                            Chemlock                                                                            Chemlock                                                                             Chemlock                                                                            Chemlock                                             402   234B  234B   205   205                  Cross-linking/curing of polyamide                                                                       --    Yes   Yes   Yes    Yes   Yes                  Cross-linking agent                                                           Acid catalyst/Amount of catalyst (parts)                                                                --    --    --    --     Form.                                                                               --                   Other than acid           --    Form. 3                                                                             --    --     --    Form. 7              Curable resin             --    --    Form. 4                                                                             Form. 5                                                                              --    --                   Air permeation coefficient of air permeation preventive                                                 55yer 4.5   3.8   3.5    3.4   3.3                  ×10.sup.-12 (cc · cm/cm.sup.2 · sec ·        cmHg) (30° C.)                                                         Young's modulus of air permeation preventive layer (MPa)                                                15    280   340   364    487   430                  (23° C.)                                                               Peeling strength of air permeation preventive layer/carcass                                             40    44    45    45     42    44                   layer (N/cm) (23° C.)                                                  Long term durability test Passed                                                                              Passed                                                                              Passed                                                                              Passed Passed                                                                              Passed               Tire air leakage performance (%/month)                                                                  3.0   2.6   2.3   2.2    2.1   2.1                  Thickness of air permeation preventive layer (min)                                                      0.50  0.05  0.05  0.05   0.05  0.05                 Mass of air permeation preventive layer (g)                                                             480   48    47    48     48    48                   Melting point of air permeation preventive layer (° C.)                                          --    160   178   175    170   170                  __________________________________________________________________________     (Note) Tire Size: 165SR13 steel radial tire.                             

                                      TABLE I-2                                   __________________________________________________________________________                         Stan-                                                                             Comp.                                                                     dard ex.                                                                          Ex. I-2                                                                            Ex. I-12                                                                           Ex. I-13                                                                           Ex. I-14                                                                           Ex. I-15                                                                            Ex. I-16                                                                            Ex.                  __________________________________________________________________________                                                             I-17                 Material of air permeation preventive layer                                                        Butyl                                                                             Alkoxyalkylated aliphatic polyamide resin                                 rubber                                                   Step of coating air permeation preventive layer                                                    --  After tire vulcanization                             Type of polyamide/Amount of polyamide (parts)                                                      --  Lucka-                                                                             Lucka-                                                                             Lucka-                                                                             Lucka-                                                                             Luckamide                                                                           Luckamide                                                                           Polymer B                                     mide 100                                                                           mide 100                                                                           mide 100                                                                           mide 100                                                                           100   100   100                  Method of bonding rubber and polyamide                                        Halogenation         --  Yes  --   --   --   --    --                         Use of adhesive      --  --   Yes  Yes  Yes  Yes   Yes   Yes                  Type of adhesive used         Chemlock                                                                           Chemlock                                                                           Chemlock                                                                           Chemlock                                                                            Chemlock                                                                            Chemlock                                           234B 234B 234B 205   205   234B                 Cross-linking/curing of polyamide                                                                  --  Yes  No   Yes  Yes  Yes   Yes   Yes                  Cross-linking agent                                                           Acid catalyst/Amount of catalyst (parts)                                                           --  Tartaric                                                                           --   Tartaric                                                                           Tartaric                                                                           Citric acid                                                                         Citric                                                                              --id                                          acid 5    acid 5                                                                             acid 5                                                                             5     5                          Other than acid      --  --   --   --   --   --    --    From. 8              Cross-linking/curing heat treatment conditions                                                     --  160° C. ×                                                             --   160° C. ×                                                             180° C. ×                                                             160° C. ×                                                              180° C.                                                                      160° C.                                                                × 10                                    5 min     5 min                                                                              10 min                                                                             min   10 min                                                                              min                  Air permeation coefficient of air permeation                                                       55  3.0  4.7  3.0  3.0  3.2   3.2   5.2                  preventive layer ×10.sup.-12 (cc ·                             cm/cm.sup.2 · sec · cmHg) (30° C.)                   Young's modulus of air permeation                                                                  15  252  145  252  330  240   318   360                  preventive layer (MPa) (23° C.)                                        Melting point of air permeation preventive                                                         --  160  152  160  160  155   157   160                  layer (° C.)                                                           Peeling strength of air permeation                                                                 40  28   32   34   35   34    34    38                   preventive layer/carcass layer (N/cm) (23° C.)                         Long term durability test                                                                          Pass                                                                              Failed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                              Passed                                                                              Passed                                        Liner                                                                         peeling                                              Tire air leakage performance (%/month)                                                             3.0 2.9  2.7  2.9  2.5  3.0   2.8   2.9                  Thickness of air permeation preventive                                                             0.50                                                                              0.05 0.05 0.05 0.05 0.05  0.05  0.05                 layer (mm)                                                                    Mass of air permeation preventive layer (g)                                                        480 47   47   48   49   48    49    48                   __________________________________________________________________________                       Stan-                                                                         dard                                                                              Comp.                                                                     ex. Ex. I-18                                                                           Ex. I-19                                                                           Ex. I-20                                                                           Ex. I-21                                                                           Ex. I-22                                                                           Ex. I-23                                                                           Ex.                                                                                Ex.                 __________________________________________________________________________                                                              1-3                 Material of air permeation preventive layer                                                      Butyl                                                                             Alkoxyalkylated aliphatic polyamide resin                                 rubber                                                     Step of coating air permeation preventive                                                        --  After tire vulcanization                               layer                                                                         Type of polyamide/Amount of                                                                      --  Polymer A                                                                          Polymer A                                                                          Polymer A                                                                          Lucka-                                                                             Lucka-                                                                             Lucka-                                                                             Lucka-                                                                             Polymer             polyamide (parts)      100  100  100  mide 100                                                                           mide 100                                                                           mide 100                                                                           mide                                                                               C*.sup.1 100        Method of bonding rubber and polyamide                                        Halogenation       --  --   --   --   --   --   --   --   --                  Use of adhesive    --  Yes  Yes  Yes  Yes  Yes  Yes  Yes  Yes                 Type of adhesive used  Chemlock                                                                           Chemlock                                                                           Chemlock                                                                           Chemlock                                                                           Chemlock                                                                           Chemlock                                                                           Chemlock                                                                           Chemlock                                   402  402  402  234B 234B 205  205  205                 Cross-linking/curing of polyamide                                                                --  Yes  Yes  Yes  Yes  Yes  Yes  Yes  Yes                 Cross-linking agent                                                           Acid catalyst/Amount of catalyst(parts)                                                          --  --   --   --   --   --   Form. 6                                                                            --   --                  Other than acid    --  Form. 1                                                                            Form. 2                                                                            Form. 3                                                                            --   --   --   Form.                                                                              Form. 1             Curable resin      --  --   --   --   Form. 4                                                                            Form. 5                                                                            --   --   --                  Cross-linking/curing heat treatment                                                              --  160° C. ×                                                             160° C. ×                                                             160 ° C. ×                                                            130° C. ×                                                             130° C.                                                                     160° C.                                                                     160° C.                                                                ×                                                                            160° C.                                                                ×             conditions             10 min                                                                             10 min                                                                             10 min                                                                             10 min                                                                             10 min                                                                             10 min                                                                             10                                                                                 10 min              Air permeation coefficient of air permeation                                                     55  4.5  4.2  4.5  3.8  3.5  3.4  3.3  4.5                 preventive layer × 10.sup.-12                                           (cc · cm/cm.sup.2 · sec · cmHg) (30°        C.)                                                                           Young's modulus of air permeation                                                                15  222  240  236  340  364  487  430  222                 preventive layer (MPa) (23° C.)                                        Peeling strength of air permeation preventive                                                    40  40   42   38   42   40   38   39   40                  layer/carcass layer (N/cm) (23° C.)                                    Long term durability test                                                                        Passed                                                                            Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Failed              Tire air leakage performance (%/month)                                                           3.0 2.6  2.5  2.6  2.3  2.2  2.1  2.1  2.6                 Thickness of air permeation preventive layer                                                     0.50                                                                              0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05                (mm)                                                                          Mass of air permeation preventive layer (g)                                                      480 48   47   47   49   50   49   49   48                  Melting point of air permeation preventive                                                       --  155  157  160  178  175  170  170  75                  layer (° C.)                                                           __________________________________________________________________________     (Note) Tire size: 165SR13 steel radial tire.                                  *.sup.1 Polymer C: Synthesized by a method similar to the Polymer B but       making the reacted nylon a nylon 6/66/610/12.                            

As explained above, according to the first aspect of the presentinvention, it is possible to obtain a pneumatic tire having an airpermeation preventive layer which enables the weight of the tire to bereduced while maintaining an excellent air pressure retention in thetire and which is superior in bonding with a rubber layer.

Examples II-1 to II-8 and Comparative Examples II-1 to II-4

Examples II-1 to II-4 and Comparative Examples II-1 to II-2 are examplesof coating a multi component copolymer polyamide resin compositionbefore vulcanization of the tire. The inner surface of a green tiremolded by an ordinary method and comprised of unvulcanized rubber ishalogenated (brush-coated with a 3.3% solution of trichloroisocyanuricacid in ethyl acetate and then dried for 2 hours) or coated with anadhesive (brush coated and dried for 2 hours), then was spray-coated bya solution comprised of a mixed solvent of 70% by weight of methanol and30% by weight of methyl ethyl ketone in which has been dissolved a multicomponent copolymer polyamide resin in a proportion of 20% by weight (inthe Examples, a curable resin and curing agent were added). This isblown on by hot air of 80° C. for 2 minutes, then vulcanized by a tirevulcanizer at 185° C. for 15 minutes at a pressure of 2.3 MPa.

Examples II-5 to II-8 and Comparative Examples II-3 to II-4 are Examplesof halogenation or coating an adhesive in the same way on the innersurface of a tire vulcanized by an ordinary method under the same typeof vulcanization conditions as above, then spray-coating it with asolution prepared in the same way as above and curing in accordance withthe nylon curing heat treatment conditions or adhesive curing conditionsshown in Table II-2.

Further, the standard Example of a tire used a butyl rubber compositionof the following formulation as an inner liner layer:

    ______________________________________                                        Formulation of Butyl Rubber Compound                                          (Unit: Parts by Weight)                                                       ______________________________________                                        Br-IIR                100                                                     Carbon black (GPF)    60                                                      Stearic acid          1                                                       Petroleum based hydrocarbon resin.sup.*1                                                            10                                                      Paraffinic process oil                                                                              10                                                      Zinc oxide            3                                                       DM                    1                                                       Sulfur                0.6                                                     ______________________________________                                         .sup.*1 Escorez 1102 made by Esso Chemical.                              

The methods of evaluation used in the following examples were asfollows:

Method for Preparation of Multi Component Copolymer Polyamide ResinSolution Used in Tire

The nylons, curable resins, curing agents, etc. shown in Tables II-1 andII-2 were dissolved in a mixed solvent of 30% by weight of methyl ethylketone and 70% by weight of methanol to give a polyamide resin/epoxyresin formulation of 30% by weight.

Preparation for Film Sample

Multi component copolymer nylon solutions of the formulations ofExamples and Comparative Examples dissolved in a proportion of 20% byweight in a mixed solvent of 70% by weight of methanol and 30% by weightof methyl ethyl ketone were formed into films by the film casting method(uniformly casting a polymer solution on an endless belt, continuouslydrying it by blowing hot air of 60 to 90° C., then peeling to form afilm). After drying, these films were allowed to stand in a 130° C.heater for 10 minutes to cure. (Film: thickness of approximately 100 μm)

Measurement of Air Permeation Coefficient of Air Permeation PreventiveLayer

See above.

Method for Measurement of Young's Modulus of Air Permeation PreventiveLayer

See above.

Method for Measurement of Melting Point

See above.

Existence of Destruction of Air Permeation Preventive Layer AfterVulcanization

The multi component copolymer polyamide resin solution was coated on agreen tire, then the tire was vulcanized. The surface of the polyamideresin layer was visually examined to determine the existence ofbubbling, flowing, or other destruction.

Method for Measurement of Peeling Strength of Air Permeation PreventiveLayer/Carcass Layer

See above.

Method for Testing Long Term Durability

See above.

Method for Testing Long Term Heat Resistance

A 165SR13 steel radial tire (rim 13×41/2-J) was used and run on a φ1707mm drum at a speed of 140 km/h at an air pressure of 250 kPa, a load of2.5 kN, and a room temperature of 45° C.

After 25,000 km, the tire was removed from the rim and the liner layerat the inside surface of the tire was visually examined. Liner layerswith cracks, visible wrinkles, or peeled or blistered liner layers werejudged as failing and those without them as passing. Note that justbefore the test run, the tire was allowed to stand for 14 days at a roomtemperature of 80° C. or more.

The test was designed to recreate on an indoor drum and evaluate as awhole the durability due to heat degradation of the liner layer.

Method for Testing Tire Air Leakage Performance

See above.

The results obtained are shown in the following Tables.

                                      TABLE II-1                                  __________________________________________________________________________    Example of Coating of Multi Component Copolymer Nylon Before                  Vulcanization of Tire                                                         (Tire Size: 165SR13 Steel Radial Tire)                                                                Comp.   Ex. Ex.  Comp.                                                                              Ex.   Ex.  Standard                                     Ex. II-1                                                                              II-1                                                                              II-2 Ex. II-2                                                                           II-3  II-4 Ex.                  __________________________________________________________________________    Material of air permeation preventive layer                                                           Multi component copolymer nylon                                                                                Butyl rubber         Step of coating air permeation preventive layer                                                       Before tire vulcanization        --                   Air permeation preventive layer/rubber bonding                                                        Halogenation treatment                                                                         Adhesive        --                   Type of adhesive        --      --  --   Chemlock                                                                           Chemlock                                                                            Chemlock                                                           205  402   234B                      Type of nylon           *.sup.1 *.sup.1                                                                           *.sup.2                                                                            *.sup.2                                                                            *.sup.1                                                                             *.sup.2                                                                            --                   Amount of nylon (parts) 100     100 100  100  100   100  --                   Curable resin/Epoxy resin*.sup.3                                                                      --      25  25   --   25    25   --                   Curing agent/dicyan diamide*.sup.4                                                                    --      10  10   --   10    10   --                   Air permeation coefficient of air permeation preventive                                               3.5     3.0 3.2  4.0  3.0   3.2  55                   layer × 10.sup.-12 (cc · cm/cm.sup.2 · sec            · cmHg) (30° C.)                                              Young's modulus of air permeation preventive layer                                                    230     450 420  210  450   420  15                   (MPa) (23° C.)                                                         Melting point of air permeation preventive layer (° C.)                                        150     180 180  85   120   120  --                   Destruction of air permeation preventive layer after                                                  Yes (bubbles)                                                                         No  No   Yes  No    No   No                   vulcanization                                                                 Peeling strength of air permeation preventive                                                         32      31  31   42   41    42   40                   layer/carcass layer (N/cm) (23° C.)                                    Long term water resistance/moisture absorption                                                        Failed  Passed                                                                            Passed                                                                             Failed                                                                             Passed                                                                              Passed                                                                             Passed               resistance                                                                    Long term durability test                                                                             Failed  Passed                                                                            Passed                                                                             Failed                                                                             Passed                                                                              Passed                                                                             Passed               Long term heat resistance test                                                                        Passed  Passed                                                                            Passed                                                                             Failed                                                                             Passed                                                                              Passed                                                                             Passed               Tire air leakage performance (%/month)                                                                2.2     1.9 2.0  2.4  1.9   2.0  3.0                  Thickness of air permeation preventive layer (mm)                                                     0.05    0.05                                                                              0.05 0.05 0.05  0.05 0.50                 Mass of air permeation preventive layer (g)                                                           47      49  48   47   49    47   480                  __________________________________________________________________________     *.sup.1 Nylon 6/66/610 made by Toray, CM4000; *.sup.2 Nylon 6/66/610/12       made by Toray, CM8000; *.sup.3 Epicoat 828: Bisphenol A diglycidyl ether      (made byShell Chemical); *.sup.4 DICY15: made by Yuka Shell Epoxy.       

                                      TABLE II-2                                  __________________________________________________________________________    Example of Coating of Multi Component Copolymer Nylon After Vulcanization     of Tire                                                                       (Tire Size: 165SR13 Steel Radial Tire)                                                                Comp.                                                                              Ex.   Ex.   Comp. Ex.  Ex.  Stan-                                        Ex. II-3                                                                           II-5  II-6  Ex. II-4                                                                            II-7 II-8 dard                 __________________________________________________________________________                                                             Ex.                  Material of air permeation preventive layer                                                           Multi component copolymer nylon                                                                                Butyl rubber         Step of coating air permeation preventive layer                                                       After tire vulcanization         --                   Air permeation preventive layer/rubber bonding                                                        Halogenation treatment                                                                         Adhesive        --                   Type of adhesive        --   --    --    Chemlock                                                                            Chemlock                                                                           Chemlock                                                           205   402  234B                      Type of nylon           *.sup.1                                                                            *.sup.1                                                                             *.sup.2                                                                             *.sup.2                                                                             *.sup.1                                                                            *.sup.2                                                                            --                   Amount of nylon(parts)  100  100   100   100   100  100  --                   Curable resin/Epoxy resin*.sup.3                                                                      --   25    25    --    25   25   --                   Curing agent/dicyan diamide*.sup.4                                                                    --   10    10    --    10   10   --                   Nylon curing heat treatment conditions or adhesive                                                    --   130° C. × 10                                                           130° C. × 10                                                           130° C.                                                                      130° C.                                                                     130° C.                                                                ×                                                                            --                   curing conditions            min   min   min   10 min                                                                             10 min                    Air permeation coefficient of air permeation preventive                                               3.5  3.0   3.2   4.0   3.0  3.2  55                   layer × 10.sup.-12 (c · cm/cm.sup.2 · sec             · cmHg) (30° C.)                                              Young's modulus of air permeation preventive layer                                                    230  450   420   210   450  420  25                   (MPa) (23° C.)                                                         Melting point of air permeation preventive layer (° C.)                                        150  180   180   85    120  120  --                   Destruction of air permeation preventive layer after                                                  Yes  No    No    Yes   No   No   No                   vulcanization                                                                 Peeling strength of air permeation preventive                                                         25   22    23    34    32   33   40                   layer/carcass layer (N/cm) (23° C.)                                    Long term Water resistance/moisture absorption                                                        Failed                                                                             Passed                                                                              Passed                                                                              Failed                                                                              Passed                                                                             Passed                                                                             Passed               resistance                                                                    Long term durability test                                                                             Failed                                                                             Passed                                                                              Passed                                                                              Failed                                                                              Passed                                                                             Passed                                                                             Passed               Long term heat resistance test                                                                        Passed                                                                             Passed                                                                              Passed                                                                              Failed                                                                              Passed                                                                             Passed                                                                             Passed               Tire air leakage performance(%/month)                                                                 2.4  2.0   2.2   2.6   2.1  2.2  3.0                  Thickness of air permeation preventive layer (mm)                                                     0.05 0.05  0.05  0.05  0.05 0.05 0.50                 Mass of air permeation preventive layer (g)                                                           47   49    48    47    49   47   480                  __________________________________________________________________________     *.sup.1 Nylon 6/66/610 made by Toray, CM4000; *.sup.2 Nylon 6/66/610/12       made by Toray, CM8000; *.sup.3 Epicoat 828: Bisphenol A diglycidyl ether      (made byShell Chemical); *.sup.4 DICY15: made by Yuka Shell Epoxy.       

As explained above, according to the second aspect of the presentinvention, it is possible to obtain a pneumatic tire having an airpermeation preventive layer which enables the weight of the tire to bereduced while maintaining an excellent air pressure retention in thetire, which is superior in bonding with a rubber layer, and which issuperior in water resistance (humidity resistance) and heat resistance).

Examples III-1 to III-16 and Comparative Examples III-1 to III-5

Examples III-1 to III-8 and Comparative Examples III-1 to III-2 areexamples of coating an alkoxyalkylated aliphatic polyamide resin beforevulcanization of the tire. The inner surface of a green tire molded byan ordinary method and comprised of unvulcanized rubber was halogenated(brush-coated with a 3.3% solution of trichloroisocyanuric acid in ethylacetate and then dried for 2 hours), then was spray-coated by a solutioncomprised of a mixed solvent of 70% by weight of methanol and 30% byweight of methyl ethyl ketone in which has been dissolved analkoxyalkylated aliphatic polyamide resin in a proportion of 20% byweight, then was dried by blowing hot air of 80° C. for 2 minutes, thenthe green tire was vulcanized by a tire vulcanizer at 185° C. for 15minutes at a pressure of 2.3 MPa.

Examples III-9 to III-16 and Comparative Examples III-3 to III-5 areexamples of halogenation in the same way on the inner surface of a tirevulcanized by an ordinary method under the same type of vulcanizationconditions as above, then spray-coating it with a solution prepared inthe same way as above and cross-linking and curing in accordance withthe cross-linking and curing conditions shown in Table III-2.

Further, the standard example of a tire used a butyl rubber compositionof the following formulation as an air permeation preventive layer:

    ______________________________________                                        Formulation of Butyl Rubber Compound                                          (Unit: Parts by Weight)                                                       ______________________________________                                        Br-IIR                100                                                     Carbon black (GPF)    60                                                      Stearic acid          1                                                       Petroleum based hydrocarbon resin.sup.*1                                                            10                                                      Paraffinic process oil                                                                              10                                                      Zinc oxide            3                                                       DM                    1                                                       Sulfur                0.6                                                     ______________________________________                                         .sup.*1 Escorez 1102 made by Esso Chemical.                              

The methods for evaluation used in the following examples were asfollows:

Method for Preparation of Alkoxyalkylated Aliphatic Polyamide ResinSolution Used in Tire

The polymers, cross-linking agents, and other additives shown in thefollowing formulations 1 to 8 were dissolved in a mixed solvent of 30%by weight of methyl ethyl ketone and 70% by weight of methanol to givepolymer concentrations of 30% by weight.

The formulations used were as shown in the following formulation 1 toformulation 8:

    ______________________________________                                                   Formul-                                                                             Formul-   Formul- Formul-                                               ation 1                                                                             ation 2   ation 3 ation 8                                    ______________________________________                                        Polymer A.sup.*1                                                                           100     100       100   --                                       Polymer B.sup.*2                                                                           --      --        --    100                                      Sulfur       1.5     --        --    1.5                                      Peroxide (di-                                                                              --      1.0       --    --                                       cumylperoxide)                                                                Sulfur-releasing-                                                                          --      --        1.5   --                                       agent (tetra-                                                                 methylthiuram                                                                 disulfide)                                                                    DM           3.0     --        --    3.0                                      M            2.0     --        --    2.0                                      MZ           2.0     --        --    2.0                                      SnCl.sub.2   1.0     --        --    1.0                                      ______________________________________                                         .sup.*1 Polymer A: Polymer A was formulated as follows in accordance with     the method described in Japanese Unexamined Patent Publication (Kokai) No     5124657, page 3, bottom right column, Production Example (2) (parts are       parts by weight).                                                        

A 500 parts amount of nylon 6 and 2000 parts of formic acid were placedin a reactor provided with a reflux cover and were fully stirred to makea homogeneous solution. A 3 parts by weight of phenol and 10 parts ofN-methylolacrylamide were added and the stirring continued for 30minutes while holding the temperature at 70° C. During this process, theN-methylolacrylamide and >NH groups included in the nylon 6 moleculecaused in a dehydrogenation condensation reaction.

Separately, 10 parts of KOH were added to 3000 parts of methanol held at60° C. and a homogeneous solution made, then 2500 parts ofpara-formaldehyde were added to cause complete dissolution. TheN-methoxymethylation reaction was ended while gradually adding this inthe above nylon 6 formic acid solution.

At this time, the temperature of the reaction system became 60 to 64° C.Further, the time until the end of the addition of themethanol-paraformaldehyde solution was made 10 to 15 minutes and thereaction was made to end in 60 minutes from the start of the addition.

The resultant reaction solution was poured into water and the targetsubstance was removed. This was fully washed with water, then dried. Theresult was a flexible substance having a good elasticity.

A 500 parts by weight of nylon 66 and 2000 parts of formic acid wereplaced in a reactor provided with a reflux cover and were fully stirredto make a homogeneous solution. A 3 parts amount of phenol and 10 partsof N-methylolacrylamide were added and the stirring continued for 30minutes while holding the temperature at 70° C. During this process, theN-methylolacrylamide and >NH groups included in the nylon 66 moleculecaused a dehydrogenation condensation reaction.

    ______________________________________                                                         Formul-                                                                             Formul-                                                                 ation 4                                                                             ation 5                                                ______________________________________                                        Luckamide 5003.sup.*1                                                                            100     100                                                Epicoat #828.sup.*2                                                                              15      30                                                 (epoxide group)                                                               Sebacic acid dihydrazide                                                                           3.5     7.5                                              (curing agent)                                                                ______________________________________                                         .sup.*1 Luckamide 5003: Dainippon Ink nylon 8/nylon 6 based                   methoxymethylated aliphatic polyamide resin (amide conversion rate of at      least 28%)                                                                    .sup.*2 Epicoat #828: Bisphenol A diglycidyl ether (Shell Chemical)      

    ______________________________________                                                         Formul-                                                                             Formul-                                                                 ation 6                                                                             ation 7                                                ______________________________________                                        Luckamide 5003     100     100                                                Hitanol 1502.sup.*1                                                                              12      --                                                 Tackirol 250-1.sup.*2                                                                            --      20                                                 Zinc oxide          3       3                                                 CR W.sup.*3         1      --                                                 ______________________________________                                         .sup.*1 Hitanol 1502: Resol type phenol resin of molecular weight of abou     800 (made by Hitachi Kasei Co.)                                               .sup.*2 Tackirol 2501: Brominated alkylphenolformaldehyde resin (made by      Taoka Kagaku Kogyo)                                                           .sup.*3 Chloroprene rubber Neoprene W: made by Showa Denko Dupont Co.    

Preparation of Film Sample

Solutions of alkoxyalkylated aliphatic polyamide resin of theformulations of Examples and Comparative Examples dissolved in aproportion of 20% by weight in a mixed solvent of 70% by weight ofmethanol and 30% by weight of methyl ethyl ketone were formed into filmsby the film casting method (uniformly casting a polymer solution on anendless belt, continuously drying it by blowing hot air of 60 to 90° C.,then peeling to form a film). After drying, these were allowed to standin a 130° C. heater for 15 minutes for a cross-linking or curingreaction. (Film: thickness of approximately 100 μm)

Measurement of Air Permeation Coefficient of Air Permeation PreventiveLayer

See above.

Method for Measurement of Young's Modulus of Air Permeation PreventiveLayer

See above.

Method for Measurement of Melting Point

See above.

Existence of Destruction of Air Permeation Preventive Layer AfterVulcanization

The alkoxyalkylated aliphatic polyamide resin solution was coated on agreen tire, then the tire was vulcanized. The surface of the polyamidewas visually examined to determine the existence of bubbling, flowing,or other destruction.

Method for Measurement of Peeling Strength of Air Permeation PreventiveLayer/Carcass Layer

See above.

Method for Testing Long Term Durability

See above.

Method for Testing Long Term Heat Resistance

See above.

Method for Testing Tire Air Leakage Performance

See above.

    ______________________________________                                        Formulation of Rubber for Tire Carcass                                                             Parts by                                                 Ingredient           weight                                                   ______________________________________                                        Natural rubber       80.0                                                     SBR 1502             20.0                                                     FEF carbon black     50.0                                                     Stearic acid         2.0                                                      Zinc oxide           3.0                                                      Sulfur               3.0                                                      Vulcanization accelerator (NS)                                                                     1.0                                                      Aromatic oil         2.0                                                      ______________________________________                                    

The results of the evaluation are shown in Table III-1 and Table III-2.

                                      TABLE III-1                                 __________________________________________________________________________                               Standard                                                                            Comp. Ex.                                                                           Comp Ex.                                                                            Ex.   Ex.   Ex.                                             ex.   III-1 III-2 III-1 III-2 III-3                __________________________________________________________________________    Material of air permeation preventive layer                                                              Butyl Alkoxyalkylated aliphatic polyamide                                           resin                                                                   rubber                                             Step of coating air permeation preventive layer                                                          --    Before tire vulcanization                    Type of polyamide/Amount of polyamide (parts)                                                            --    Luckamide                                                                           Luckamide                                                                           Polymer A                                                                           Polymer                                                                             Polymer A                                             100   100   100   100   100                  Cross-linking or curing of polyamide                                                                     --    No    Yes   Yes   Yes   Yes                  Cross-linking agent        --    --    Citric acid 5                                                                       --    --    --                   Acid catalyst/Amount of catalyst (parts)                                                                 --    --    --    Form. 1                                                                             Form.                                                                               Form. 3              Other than acid            --    --    --    --    --    --                   Curable resin                                                                 Air permeation coefficient of air permeation preventive layer                                            55imes.                                                                             4.7   3.0   4.5   4.2   4.5                  10.sup.-12 (cc · cm/cm.sup.2 · sec · cmHg) (at     30° C.)                                                                Young's modulus of air permeation preventive layer (MPa)                                                 15    145   300   275   290   280                  (23° C.)                                                               Melting point of air permeation preventive layer (° C.)                                           --    152   160   155   157   160                  Destruction of air permeation preventive layer after                                                     No    Yes   Yes   No    No    No                   vulcanization                    (bubbles)                                                                           (bubbles)                              Peeling strength of air permeation preventive layer/carcass                                              40    33    35    39    38    38                   layer (N/cm) (23° C.)                                                  Long term water resistance and moisture absorption                                                       Passed                                                                              Failed                                                                              Passed                                                                              Passed                                                                              Passed                                                                              Passed               resistance test                                                               Long term durability test  Passed                                                                              Passed                                                                              Failed                                                                              Passed                                                                              Passed                                                                              Passed               Long term heat resistance test                                                                           Passed                                                                              Failed                                                                              Failed                                                                              Passed                                                                              Passed                                                                              Passed               Tire air leakage performance (%/month)                                                                   3.0   2.7   1.9   2.6   2.5   2.6                  Thickness of air permeation preventive layer(mm)                                                         0.50  0.05  0.05  0.05  0.05  0.05                 Mass of air permeation preventive layer (g)                                                              480   47    48    48    47    47                   __________________________________________________________________________                               Stan- Ex.   Ex.   Ex.   Ex.   Ex.                                             dard ex.                                                                            III-4 III-5 III-6 III-7 III-8                __________________________________________________________________________    Material of air permeation preventive layer                                                              Butyl Alkoxyalkylated aliphatic polyamide                                           resin                                                                   rubber                                             Step of coating air permeation preventive layer                                                                Before tire vulcanization                    Type of polyamide/Amount of polyamide (parts)                                                            --    Luckamide                                                                           Luckamide                                                                           Luckamide                                                                           Luckamide                                                                           Polymer B                                             100   100   100   100   100                  Cross-linking or curing of polyamide                                                                     --    Yes   Yes   Yes   Yes   Yes                  Cross-linking agent        --    --    --    --    --    --                   Acid catalyst/Amount of catalyst (parts)                                                                 --    --    --    Form. 6                                                                             Form.                                                                               Form. 8              Other than acid            --    Form. 4                                                                             Form. 5                                                                             --    --    --                   Curable resin                                                                 Air permeation coefficient of air permeation preventive layer                                            55imes.                                                                             3.8   3.5   3.3   3.5   4.8                  10.sup.-12 (cc · cm/cm.sup.2 · sec · cmHg) (at     30° C.)                                                                Young's modulus of air permeation preventive layer (MPa)                                                 15    340   364   487   430   383                  (23° C.)                                                               Melting point of air permeation preventive layer (° C.)                                           --    178   175   170   170   160                  Destruction of air permeation preventive layer after                                                     No    No    No    No    No    No                   vulcanization                                                                 Peeling strength of air permeation preventive layer/carcass                                              40    37    37    35    36    37                   layer (N/cm) (23° C.)                                                  Long term water resistance and moisture absorption                                                       Passed                                                                              Passed                                                                              Passed                                                                              Passed                                                                              Passed                                                                              Passed               resistance test                                                               Long term durability test  Passed                                                                              Passed                                                                              Passed                                                                              Passed                                                                              Passed                                                                              Passed               Long term heat resistance test                                                                           Passed                                                                              Passed                                                                              Passed                                                                              Passed                                                                              Passed                                                                              Passed               Tire air leakage performance (%/month)                                                                   3.0   2.3   2.2   2.1   2.2   2.8                  Thickness of air permeation preventive layer (mm)                                                        0.50  0.05  0.05  0.05  0.05  0.05                 Mass of air permeation preventive layer (g)                                                              480   49    50    49    49    48                   __________________________________________________________________________     (Note) Tire size: 165SR13 steel radial tire.                             

                                      TABLE III-2                                 __________________________________________________________________________                               Stan-                                                                              Comp. Comp. Comp. Ex.    Ex.                                             dard ex.                                                                           Ex. III-3                                                                           Ex. III-4                                                                           Ex. III-5                                                                           III-9  III-10               __________________________________________________________________________    Material of air permeation preventive layer                                                              Butyl                                                                              Alkoxyalkylated aliphatic polyamide                                           resin                                                                    rubber                                             Step of coating air permeation preventive layer                                                          --   After tire vulcanization                      Type of polyamide/Amount of polyamide (parts)                                                            --   Luckamide                                                                           Luckamide                                                                           Polymer C*.sup.1                                                                    Polymer                                                                              Polymer A                                            100   100   100   100    100                  Cross-linking or curing of polyamide                                                                     --   No    Yes   Yes   Yes    Yes                  Cross-linking agent                                                           Acid catalyst/Amount of catalyst (parts)                                                                 --   --    Tartaric acid                                                                       --    --                                                                5                                       Other than acid            --   --    --    Form. 1                                                                             Form.                                                                                Form. 2              Curable resin              --   --    --    --    --     --                   Cross-linking/curing heat treatment conditions                                                           --   --    150° C. × 5                                                            160° C. ×                                                              160° C. ×                                                        10     160  C. ×                                                               10                                                         min   min   min    min                  Air permeation coefficient of air permeation preventive layer                                            55imes.                                                                            4.7   5.3   4.5   4.5    4.2                  10.sup.-12 (cc · cm/cm.sup.2 · sec · cmHg) (at     30° C.)                                                                Young's modulus of air permeation preventive layer (MPa)                                                 15   145   252   223   222    240                  (23° C.)                                                               Peeling strength of air permeation preventive layer/carcass                                              40   25    28    35    35     32                   layer (N/cm) (23° C.)                                                  Long term water resistance and moisture absorption                                                       Passed                                                                             Failed                                                                              Passed                                                                              Passed                                                                              Passed Passed               resistance test                                                               Long term durability test  Passed                                                                             Passed                                                                              Failed                                                                              Passed                                                                              Passed Passed               Long term heat resistance test                                                                           Passed                                                                             Failed                                                                              Failed                                                                              Failed                                                                              Passed Passed               Tire air leakage performance (%/month)                                                                   3.0  2.7   2.9   2.6   2.6    2.5                  Thickness of air permeation preventive layer (mm)                                                        0.50 0.05  0.05  0.05  0.05   0.05                 Mass of air permeation preventive layer (g)                                                              480  47    47    48    48     47                   Melting point of air permeation preventive layer (° C.)                                           --   152   160   75    155    157                  __________________________________________________________________________                               Stand-                                                                             Ex.  Ex.  Ex.  Ex.  Ex.  Ex.                                             dard ex.                                                                           III-11                                                                             III-12                                                                             III-13                                                                             III-14                                                                             III-15                                                                             III-16               __________________________________________________________________________    Material of air permeation preventive layer                                                              Butyl                                                                              Alkoxyalkylated aliphatic polyamide                                           resin                                                                    rubber                                             Step of coating air permeation preventive layer                                                          --   After tire vulcanization                      Type of polyamide/Amount of polyamide (parts)                                                            --   Polymer A                                                                          Lucka-                                                                             Lucka-                                                                             Lucka-                                                                             Lucka-                                                                             Polymer B                                            100  mide 100                                                                           mide 100                                                                           mide 100                                                                           mide                                                                               100                  Cross-linking or curing of polyamide                                                                     --   Yes  Yes  Yes  Yes  Yes  Yes                  Cross-linking agent                                                           Acid catalyst/Amount of catalyst (parts)                                      Other than acid            --   Form. 3                                                                            --   --   Form. 6                                                                            Form.                                                                              Form. 8              Curable resin              --   --   Form. 4                                                                            Form. 5                                                                            --   --   --                   Cross-linking/curing heat treatment conditions                                                           --   160° ×                                                                130° C. ×                                                             130° C.                                                                     160° C.                                                                     160° C.                                                                ×                                                                            160° C.                                                                ×                                              10 min                                                                             10 min                                                                             10 min                                                                             10 min                                                                             10 min                                                                             10 min               Air permeation coefficient of air permeation preventive layer                                            55imes.                                                                            4.5  3.1  3.5  3.3  3.5  4.8                  10.sup.-12 (cc · cm/cm.sup.2 · sec · cmHg) (at     30° C.)                                                                Young's modulus of air permeation preventive layer (MPa)                                                 15   236  340  364  417  430  316                  (23° C.)                                                               Peeling strength of air permeation preventive layer/carcass                                              40   35   22   23   22   24   36                   layer (N/cm) (23° C.)                                                  Long term water resistance and moisture absorption                                                       Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed               resistance test                                                               Long term durability test  Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed               Long term heat resistance test                                                                           Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed                                                                             Passed               Tire air leakage performance (%/month)                                                                   3.0  2.6  2.3  2.2  2.1  2.2  2.8                  Thickness of air permeation preventive layer (mm)                                                        0.50 0.05 0.05 0.05 0.05 0.05 0.05                 Mass of air permeation preventive layer (g)                                                              480  47   49   50   49   49   48                   Melting point of air permeation preventive layer (° C.)                                           --   160  178  175  170  170  160                  __________________________________________________________________________     (Note) Tire size: 165SR13 steel radial tire.                                  *.sup.1 Polymer C: Synthesized by a method similar to the Polymer B but       making the reacted nylon a nylon 6/66/610/12.                            

As explained above, according to the third aspect of the presentinvention, it is possible to obtain a pneumatic tire having an airpermeation preventive layer in which the weight of the tire can bereduced in while maintaining an excellent air pressure retention in thetire, which is superior in bonding with a rubber layer, and which issuperior in water resistance (resistance to humidity) and heatresistance.

Examples IV-1 to IV-5 and Comparative Examples IV-1 to IV-3

Examples IV-1 to IV-3 and Comparative Examples IV-1 to IV-3 are examplesof coating a vinylidene chloride resin composition after vulcanizationof the tire. The inner surface of a tire vulcanized by a tire vulcanizerat 185° C. for 15 minutes at a pressure of 2.3 MPa by an ordinary methodwas halogenated (brush-coated with a 3.3% solution oftrichloroiso-cyanuric acid in ethyl acetate and then dried for 2 hours)or coated with an adhesive (brush coated with LORD Chemlock 205 anddried for 2 hours), then was spray-coated by a solution comprised of amixed solvent of 35% by weight of toluene and 65% by weight of methylethyl ketone in which has been dissolved a vinylidene chloride resin ina proportion of 20% by weight, then was dried by blowing hot air of 80°C. for 2 minutes to form the air permeation preventive layer.

Further, Example IV-4 is an example of the case of coating a vinylidenechloride resin composition before vulcanization of the tire. The innersurface of a green tire molded by an ordinary method and comprised ofunvulcanized rubber was halogenated in the same way as above, then wasspray-coated with a solution prepared in the same way as above and driedin the same way as above. The green tire was then vulcanized by a tirevulcanizer under similar vulcanization conditions.

Further, the standard Example of a tire used a butyl rubber compositionof the following formulation as an inner liner layer:

    ______________________________________                                        Butyl Rubber Formulation                                                      (Unit: Parts by Weight)                                                       ______________________________________                                        Br-IIR.sup.*1         100                                                     Carbon black (GPF).sup.*2                                                                           60                                                      Stearic acid          1                                                       Petroleum based hydrocarbon resin.sup.*3                                                            10                                                      Paraffinic process oil                                                                              10                                                      Zinc oxide            3                                                       DM                    1                                                       Sulfur                0.6                                                     ______________________________________                                         .sup.*1 BrIIR: Exxon Bromobutyl 2244, Exxon Chemical                          .sup.*2 GPF: Seast V, Tokai Carbon                                            .sup.*3 Escorez 1102, Esso Chemical                                           .sup.*4 Paraffinic process oil: Machine Oil 22, Showa Shell Sekiyu       

The methods of evaluation used in the following examples were asfollows:

Solubility

The vinylidene chloride resin was added to 10 cc of a mixed solventcomposed of methyl ethyl ketone and toluene in a 63:35 ratio by weightto give 20% by weight. This was then stirred. Samples dissolving within30 to 60 minutes were indicated by a "o" mark and those not dissolvingby an "x" mark.

Measurement of Air Permeation Coefficient of Air Permeation PreventiveLayer

According to JIS K7126 "Test Method of Gas Permeability of Plastic Filmsand Sheets (Method A)".

Test piece: Film samples (I) (sheets of thickness of approximately 100μm prepared by dissolving 20% by weight of vinylidene chloride resin inmixed solvent of methyl ethyl ketone/toluene=65/35 (ratio by weight),spreading the result on glass using a doctor blade, drying at ordinarytemperature, and further drying under vacuum).

Test gas: Air (N₂ :O₂ =8:2)

Test temperature: 30° C.

Method for Measurement of Young's Modulus of Film

See above.

Method for Measurement of Softening Point of Air Permeation PreventiveLayer

Using the same method of preparation as with the measurement of the airpermeation coefficient, sheets of a thickness of about 1 mm wereprepared. These were superposed to a thickness of 5 mm and then a TMAwas used for measurement at a load of 5 g, a rate of temperature rise of10° C./min, and the compression method. The point of inflexion was usedas the softening point.

Method for Testing Long Term Water Resistance and Moisture AbsorbingResistance

See above.

Method for Testing Long Term Durability

See above.

Method for Testing Long Term Heat Resistance

See above.

Method for Testing Tire Air Leakage Performance

See above.

    ______________________________________                                        Formulation of Rubber for Tire Carcass                                                             Parts by                                                 Ingredient           weight                                                   ______________________________________                                        Natural rubber       80.0                                                     SBR 1502             20.0                                                     FEF carbon black     50.0                                                     Stearic acid         2.0                                                      Zinc oxide           3.0                                                      Sulfur               3.0                                                      Vulcanization accelerator (NS)                                                                     1.0                                                      Aromatic oil         2.0                                                      ______________________________________                                    

Method of Halogenation Treatment

The entire inner surface of a green tire before vulcanization or a tireafter vulcanization was coated with a solution of 3.3% oftrichloroisocyanuric acid in ethyl acetate then was allowed to stand atordinary temperature for at least 3 hours for halogenation.

The results of Examples IV-1 to IV-3 of the case of halogenation of theinner surfaces of vulcanized tires, Example IV-4 of the case ofhalogenation of the inner surface of an unvulcanized green tire, andExample IV-5 of the case of treatment of the inner surface of a tireafter vulcanization by an adhesive (LORD Chemlock 205) are shown inTable IV-1.

                                      TABLE IV-1                                  __________________________________________________________________________                  Ex.  Ex.  Ex.  Ex.   Ex.  Comp.                                                                              Comp. Comp. Compara-                           IV-1 IV-2 IV-3 IV-4  IV-5 IV-1 IV-2  IV-3  tive                 __________________________________________________________________________                                                             tire                 Material                                                                           Main compo-                                                                            Vinylidene chloride polymer                Butyl rubber         of air                                                                             nent                                                (tie rubber          perme-                                                                             Copolymer                                                                              Acrylonitrile                  Vinyl Acryl inter-               ation                                                                              comp.                                   chloride                                                                            ester posted)              preven-                                                                            Copolymeri-                                                                            15   30   50   30    30   3    15    15                         tive zation mol %                                                             layer                                                                         Solubility    ∘                                                                      ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                      x    ∘                                                                       ∘                                                                       --                   Air permeation coefficient ×                                                          0.11 0.35 1.01 0.35  0.35 0.08 1.30  0.90  55                   10.sup.-12 cc · cm/cm.sup.2 ·0 sec ·               cmHg (at 30° C.)                                                       Young's modulus (MPa)                                                                       1.8  2.0  5.0  2.0   2.0  5.0  3.5   4.5   15                   Softening point                                                                             110  130  180  130   130  200  68    70    --                   The air leakage                                                                             0.33 0.63 1.3  0.63  0.63 0.22 2.0   1.4   3.0                  performance (%/month)                                                         Long term durability test                                                                   ∘                                                                      ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                      ∘                                                                      x     x     ∘        Long term heat resistance                                                                   ∘                                                                      ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                      ∘                                                                      x     x     ∘        test                                                                          Long term-water resistance                                                                  ∘                                                                      ∘                                                                      ∘                                                                      ∘                                                                       ∘                                                                      ∘                                                                      x     x     ∘        test                                                                          Weight and thickness of                                                                     19 g/20                                                                            18 g/20                                                                            17 g/20                                                                            18 g/20                                                                             18 g/20                                                                            20 g/20                                                                            20 g/20                                                                             19 g/20                                                                             480 g/500            air permeation preventive                                                                   μm                                                                              μm                                                                              μm                                                                              μm μm                                                                              μm                                                                              μm μm μm                layer                                                                         Method of treatment of                                                                      Haloge-                                                                            Haloge-                                                                            Haloge-                                                                            Haloge-                                                                             Adhesive                                                                           Haloge-                                                                            Haloge-                                                                             Haloge-                    inner surface of tire                                                                       nation of                                                                          nation of                                                                          nation of                                                                          nation of                                                                           treatment                                                                          nation of                                                                          nation of                                                                           nation of                                vulcan-                                                                            vulcan-                                                                            vulcan-                                                                            unvulcan-                                                                           of vulcan-                                                                         vulcan-                                                                            vulcan-                                                                             vulcan-                                  ized inner                                                                         ized inner                                                                         ized inner                                                                         ized inner                                                                          ized inner                                                                         ized inner                                                                         ized inner                                                                          ized inner                               surface                                                                            surface                                                                            surface                                                                            surface                                                                             surface                                                                            surface                                                                            surface                                                                             surface                    __________________________________________________________________________     (Note) The test fire was a size 165SR13 steel radial tire.               

As explained above, according to the fourth aspect of the presentinvention, it is possible to obtain a pneumatic tire having an airpermeation preventive layer which enables the weight of the tire to bereduced while maintaining an excellent air pressure retention in thetire, which is superior in bonding with a rubber layer, and which issuperior in water resistance (humidity resistance) and heat resistance).

We claim:
 1. A process for producing a pneumatic tire having, as an airpermeation preventive layer laminated through an adhesive, a thin filmof an aliphatic polyamide resin obtained by cross-linking by heattreatment of, in the presence of an acid catalyst, at least onealiphatic polyamide resin wherein at least part of the amide groupsthereof are modified with alkoxyalkyl groups, said processcomprising:spraying or coating an adhesive to the surface of a carcasslayer of a vulcanized tire or the surface of a rubber layer provided atthe surface of the carcass layer; and then spraying or coating theadhesive surface with a solution comprising (a) a liquid compositioncontaining at least one aliphatic polyamide resin wherein at least apart of the amide groups thereof are modified with alkoxyalkyl groupsand (b) an acid catalyst, followed by heating to form the thin film ofthe aliphatic polyamide resin.
 2. The process for producing a pneumatictire according to claim 1, wherein the air permeation preventive layerhas a melting point of at least 80° C., an air permeation coefficient of25×10⁻¹² cc·cm/cm² ·sec·cmHg (at 30° C.) or less, and a Young's modulusof 1 to 500 MPa.
 3. The process for producing a pneumatic tire accordingto claim 1, wherein the adhesive is a phenol resin adhesive, achlorinated rubber adhesive or an isocyanate adhesive.
 4. The processfor producing a pneumatic tire according to claim 1, wherein the acidcatalyst is at least one acid selected from the group consisting ofcitric acid, tartaric acid, glutamic acid, lactic acid, itaconic acid,boric acid, maleic acid and oxalic acid.
 5. The process for producing apneumatic tire according to claim 4, wherein the amount of the acidcatalyst is from 3 to 5 parts by weight based on 100 parts by weight ofthe modified aliphatic polyamide.
 6. A process for producing a pneumatictire having, as an air permeation preventive layer laminated through anadhesive, a thin film of an aliphatic polyamide resin obtained bycross-linking by heat-treatment of, in the presence of a cross-linkingagent, at least one aliphatic polyamide resin wherein at least part ofthe amide groups thereof are modified with alkoxyalkyl groups, saidprocess comprising:spraying or coating an adhesive to the surface of acarcass layer of a vulcanized tire or the surface of a rubber layerprovided at the surface of the carcass layer; and then spraying orcoating the adhesive surface with a solution comprising (a) a liquidcomposition containing at least one aliphatic polyamide resin wherein atleast a part of the amide groups thereof are modified with alkoxyalkylgroups and (b) a cross-linking agent, followed by heating to form thethin film of the aliphatic polyamide resin, said cross-linking agentbeing an organic halogen donor or an inorganic halogenated substance. 7.A process for producing a pneumatic tire having, as an air permeationpreventive layer laminated through an adhesive, a thin film of analiphatic polyamide resin obtained by cross-linking by heat treatmentof, in the presence of a cross-linking agent, at least one aliphaticpolyamide resin wherein at least part of the amide groups thereof aremodified with alkoxyalkyl groups, said process comprising:spraying orcoating an adhesive to the surface of a carcass layer of a vulcanizedtire or the surface of a rubber layer provided at the surface of thecarcass layer; and then spraying or coating the adhesive surface with asolution comprising (a) a liquid composition containing at least onealiphatic polyamide resin wherein at least a part of the amide groupsthereof are modified with alkoxyalkyl groups and (b) a cross-linkingagent, followed by heating to form the thin film of the aliphaticpolyamide resin, said cross-linking agent being sulfur, asulfur-releasing compound or a rubber vulcanization accelerator.